Hello there,

Here is your answer,

5x-40=4x-90

we move all terms to the left:

40x+80-(5x+40)

we get rid of parentheses

4x-5x-40+80=0

we add all the numbers together

-1x+40=0

we move all terms containing x to the 1

-x=-40

x=-40/1

[x= + 40]

After getting value of x you can put with 8x

8x =?                                  : .let x = 40

8 (40) = 320 ans

Hope this will help.

Thank you :)