Question

5a - (8-a) = 4a - 10

Answer 1

I assume you're trying to find the value of a:
5a-(8-a) = 4a -10
5a-8+a=4a-10
get all of the a values on one side and the constants on the other:
5a+a-4a =-10+8
2a=-2
a=-1
you can check the answer by substituting in -1 for a:
5(-1)-(9)) = 4(-1) -10

-5-9=-4-10
-14 = -14