50 + 30z = 250 + 10z combine like terms by subtracting 10z from both sides and subtracting 50 from both sides.
20z = 200. Divide each side by 20
Z = 10.
To ensure you're correct, plug 10 back into the equation.
50 + 30(10) = 250 + 10(10). Simplify.
350 = 350.
10 is the correct answer.