Question

Please answer quickly:

Answer 1

Start by adding b to both sides:

$aby = b+c$

Divide both sides by ab:

$y = \dfrac{b+c}{ab}$

This means that we must impose that $ab\neq 0$ which means that neither a nor b can be zero.

Answer 2

You have to move variables on one side and constants on the other   aby - b + b = c + b aby = c + b y = (c + b)/ab