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

Luke started a weight-loss program. the first week, he lost x pounds. the second week, he lost pounds less than times the pounds he lost the first week. the third week, he lost 1 pound more than of the pounds he lost the first week. liam started a weight-loss program when luke did. the first week, he lost 1 pound less than times the pounds luke lost the first week. the second week, he lost 4 pounds less than times the pounds luke lost the first week. the third week, he lost pound more than times the pounds luke lost the first week.