Alrighty I've got you on this Gaburiera-chan!
You start off with:
-8(8 - x) = 4/5(x + 10)
Let's distribute the -8 and the 4/5:
-64 - 8x = 4/5x + 8
Now we can add 64 on both sides:
-8x = 4/5x + 72
Almost forgot about those "x" like terms haha:
-36/5x = 72
Divide -36/5 (or -7.2) on both sides and... your answer should be:
x= -10