First, distribute the 8 across what is in the parentheses, then subtract 56 from both sides, then divide both sides by -8 to get positive y:
\(8(7-y) = -24\qquad\qquad\text{The original question}\\ 8\times 7 - 8\times y = -24\qquad\text{Distribute the 8 across the inside of the parentheses}\\ 56-8y=-24\qquad\qquad\quad\text{Simplify}\\ -8y=-80\qquad\qquad\qquad\text{Subtract 56 from both sides}\\ y=-10\qquad\qquad\qquad\qquad\text{Divide by -8 on both sides}\)
So, your solution is y = -10