Is 5x-7.8 = 20.2 5.6?

Is 5x-7.8 = 20.2 5.6?

yes
5x-7.8=20.2
5x=20.2+7.8
5x=28
x=28÷5
x=5.6

8/7+12/5x=6

8/7+12/5x=6
12/5x=6-8/7=36/7
Then x = 36 / 7 * 5 / 12 = 15 / 7

2.8: x = 1.4 of 10, 5x of 6 + 1 of 3 = 7 of 20

2.8: x = 1.4 out of 10
1.4x=2.8x10
1.4x=28
x=28÷1.4
x=20
5 / 6 x + 1 / 3 = 7 / 20 times 60
50x+20=21
50x=21-20
50x=1
x=1/50
If you don't understand this question, you can ask,

-7x-【 4x+6（ 2x-8） +6】

Original formula = - 7x-4x-6 (2x-8) - 6
=-11x-12x+48-6
=-23x+42

-(a ^ 2-5a-2) + 3 (- 3A + 2a-7) simplification

-(a²-5a-2)+3(-3a+2a-7)
=-a²+5a+2-9a+6a-21
=-a²-4a-19
=-(a²+4a+19)

The two trains leave at the same time. The speed of the local train is two-thirds of that of the express train. The two trains meet six hours after leaving and continue to move on. The express train arrives several hours earlier than the local train

6 △ 2 / 3 = 9 hours
The slow train will take another nine hours
6 × 2 / 3 = 4 hours
The express will take four hours
9-4 = 5 hours
A: the express train is five hours earlier than the local train

How to transform rectangular coordinate equation y = x into polar coordinate

The transformation relationship between rectangular coordinate system and polar coordinate system is as follows:
x=rcosa,
y=rsina.
So y = x has:
rcosa=rsina
cosa=sina=cos(2kπ+π/2-a)
So a = 2K π + π / 2-a
That is: a = k π + π / 4

There are 120 tons of cement on the construction site. 40% of the total is transported in the first day and 30% in the second day. How many tons are transported in two days? How many tons are left?

120 × (40% + 30%) = 120 × 0.7 = 84 (tons) 120-84 = 36 (tons) a: a total of 84 tons were transported in two days, and 36 tons were left

Given OA vector = (6, - 2) ob vector = (- 1,2) if OC vector is perpendicular to ob vector and BC vector is parallel to OA vector, find BC vector and the angle between BC and ob vector

Let C (x, y) ∵ OC vector be perpendicular to ob vector ∵ - x + 2Y = 0. (1) ∵ BC vector be parallel to OA vector, BC vector = (x + 1, Y-2) ∵ 6 (Y-2) - (- 2) (x + 1) = 0x + 3Y = 5. (2) the solution is: x = 2, y = 1, that is, C (2,1) BC vector = (3, - 1) cosine of the angle between BC and ob vector = (3, - 1) (- 1,2) / [√ 10 √ 5] = - 2 /

A batch of yellow sand was transported by three vehicles of a, B and C. vehicle a carried 5 / 2 of the total; vehicle B carried 25% of the total; vehicle C carried 30 tons more than vehicle B
How many tons of yellow sand are there?

30÷[1-(2/5-1/4-1/4)]
=30÷1/10
=300