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
in which step did the student first make an error? (5 points)
step 4
step 3
step 2
step 1