Question

The work of a student to solve a set of equations is shown:

Equation A: y = 15 − 2z
Equation B: 3y = 3 − 4z


Step 1: −3(y) = −3(15 − 2z) [Equation A is multiplied by −3.]
3y = 3 − 4z [Equation B]
Step 2: −3y = 15 − 2z [Equation A in Step 1 is simplified.]
3y = 3 − 4z [Equation B]
Step 3: 0 = 18 − 6z [Equations in Step 2 are added.]
Step 4: 6z = 18
Step 5: z = 3