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?



Step1

Step 2

Step 3

Step 4