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

If you would like to solve a set of equations, you can do this using the following steps:

equation a: y = 15 - 2z       /*(-2)
equation b: 2y = 3 - 4z

-2y = (-2) * (15 - 2z)
-2y = -30 + 4z
2y = 3 - 4z

The mistake was made at the step 2: −2y = 15 − 2z [equation a in step 1 is simplified.]. The correct simplification would be -2y = -30 + 4z. 

answer: the 4 kilogram bag

step-by-step explanation: this is because if you divide the number of kilograms into the total it will tell you how much each individual kilogram would be worth. 2 kilos is 7 and change 3 would be around 6 ish and the 4 kilo would be 4.6 and change and the 5 kilos would be like 4.88