How to solve the equation of 10x + 6 * (15-x) = 138

How to solve the equation of 10x + 6 * (15-x) = 138

10x+6*(15-x)=138
10x+90-6x=138
10x-6x=138+90
4x=48
x=48÷4
x=12

How to solve the equation of X-15 = y + 6, X-7 = 8y?

x-15=y+6 ①
x-7=8y ②
② The results are as follows
x=8y+7
By substituting x = 8y + 7 into (1), we get the following result:
8y+7-15=y+6
8y-y=6+15-7
y=2
Substituting y = 2 into (2), we get the following result:
x-7=8×2
x=23
therefore
x=23
y=2.

Solving binary linear equations (19:18:19:14)
Given the quadratic equation x-2y + 3 = 0, and X, y are opposite numbers, find the value of X, y

The quadratic equation of two variables x-2y + 3 = 0, and X and y are opposite to each other
That is x = - Y
x-2y+3=0
-y-2y+3=0
-3y=-3
y=1
x=-y=-1

Mathematics in grade one uses equations to solve problems, please answer in detail, thank you! (7 21:13:54)
There are some cards marked with 5, 10, 15 and 20. The number on the last card is always 5 larger than that on the previous card. Xiao Ming gets three adjacent cards, and the sum of the numbers on the cards is 255. What are the numbers on the three cards Xiao Ming takes?

First of all, if the second card Xiao Ming gets is x, then the first card is X-5 and the third card is x + 5
From the meaning of the title, we can get: X-5 + X + X + 5 = 255
The solution is: x = 85
So the numbers on the three cards Xiao Ming got were 80, 85 and 90 respectively