What is the value of z if y = 2 in the formula 2z + 5y = 9?
2z + 5y = 9. If y = 2, then 2z + 5 × 2 = 9. 2z + 10 = 9. Subtract 10 from each side, giving 2z = -1. Divide both sides by 2, z = -0.5.