Solve the equation for the indicated variable: y^2 - ay + 8by - 8ab = 0 for y

y^2 - ay + 8by - 8ab = 0      factor by "grouping"

y(y - a) + 8b(y - a)  = 0    rewrite as....

(y - a)(y + 8b)  = 0    and setting each factor to 0, we have that......

y = a   or   y = -8b