Later, the boss said that today's special price was only 25 yuan, so he asked the waiter to return 5 yuan. The waiter hid 2 yuan and gave them 1 yuan. 10-1 = 9, which means that each person gave 9 yuan, 3 * 9 = 27 yuan, plus the 2 yuan hidden by the waiter, a total of 29 yuan. What about the remaining 1 yuan?

Later, the boss said that today's special price was only 25 yuan, so he asked the waiter to return 5 yuan. The waiter hid 2 yuan and gave them 1 yuan. 10-1 = 9, which means that each person gave 9 yuan, 3 * 9 = 27 yuan, plus the 2 yuan hidden by the waiter, a total of 29 yuan. What about the remaining 1 yuan?

First of all, the 9 yuan spent by each person already includes the 2 yuan hidden by the waiter (that is, the preferential price of 25 yuan + 2 yuan hidden by the waiter = 27 yuan = 3 * 9 yuan)

For three people, 10 yuan for each person, 30 yuan for the owner, 5 yuan for discount, 2 yuan for the waiter, 3 yuan for each person, 9 yuan for each person, 27 yuan plus
Waiter 2 yuan is 29 yuan, 30 minus 29 yuan, who has 1 yuan

The problem is that three people paid 27 yuan for 9 yuan each. The shopkeeper collected 25 yuan, and the waiter hid 2 yuan, just 27 yuan

Five jiao plus six yuan five jiao equals seven yuan, right

Yes

What is 1 + 2?

It's three!

If a = {a | k * 360, K belongs to Z}, B = {B | B = k * 180, K belongs to Z}, C = {y | y = k * 90, K belongs to Z}, then the following relation is correct
A A=B=C
B a = B belongs to C
C belongs to B belongs to a
D a belongs to B and C

D because 360 and 180 are even multiples of 90, and there are odd multiples of 90, a and B are included in C
360 is an even multiple of 180, and there are also odd multiples of 180, so a is included in B, so a belongs to B and C

If the terminal edges of angles α and β are opposite extension lines, then α = (2k + 1) · 180 ° + β, K ∈ Z can be 180 ° K + β, K ∈ Z

No
Because here the coefficient of K has to be odd
If it is an even number, the final edges coincide

Why is the symmetry axis of sine function 2 / Pie + K pie instead of 2 / Pie + 2K pie

X = π / 2 is an axis of symmetry adjacent to it on the right
X = 3 π / 2 of is also an axis of symmetry
The distance between the axes of is π, which is the half cycle of the sine function
And every half cycle is the next axis
The axis of symmetry of sine function is
X = Pie / 2 + K pie, K ∈ Z
Not x = faction / 2 + 2K faction

The monotone interval of sine type function generally has 2K Π - Π / 2 ＜ x + Π / 4 ＜ 2K Π + Π / 2, but the number after 2K Π is different. What determines them?

Consider the function as a composite function of y = 2sinu, u = π / 4 - X,
Because u = π / 4 - x is a decreasing function, when 2sinu is an increasing function, 2Sin (π / 4 - x) is a decreasing function,
When sin 2 u is a decreasing function, sin 2 u is a decreasing function

The sum of solutions of the equations 3kx 2Y = 6K and 2XY = 8 of X and Y is 10

This is three equations, three unknowns
x+y=10
And the two equations you mentioned
Use the latter two equations to get the solution of the equation, and then bring it to the first equation to get the answer

Given that the solution of the system of equations 3kx + 2Y = 6k2x + y = 8 satisfies the equation x + y = 10, find K

∵ x + y = 10 (1), 2x + y = 8 (2), from (1) - 2 we get x = - 2, y = 12, substituting the values of X and Y into 3kx + 2Y = 6K, we get: - 6K + 24 = 6K, we get k = 2