Question

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

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

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

In which step did the student first make an error?

Answer 1

please help?

Answer 2

notice how the student went from −2(15 − 2z) in step 1 to 15 − 2z in step 2

this is an error in distribution. the proper result from distributing the -2 would be
-30 + 4z