Here's a system of equations I'm really stuck on:
x=4/3y
4/3x=7+y
Solve for y
Does "4/3y" mean (4/3)y? Assuming that and "4/3x" means (4/3)x, just replace the x in the second equation by (4/3)y:
(4/3)x= (4/3)(4/3)y= (16/9)y= 7+ y. Now subtract y from both sides.
(If "4/3y" means 4/(3y) and "4/3x" means 4/(3x), much the same: 4/(3(4/3y))= (4/3)(3y/4)= y= 7+ y which is impossible.)