I'm way beyond this but just starting the school year i'm having a complete brain block about how to do this.

how would i solve this equation?

5/x^2 = 8/(10+x)^2

i can expand the demoninator on the right, but then... i have no clue where to go. this is preventing me from solving a larger problem and it's driving me crazy that i don't know what to do. any advice?