Question

From the set {30, 42, 84}, use substitution to determine which value of x makes the equation true.

2,520 + x = 60

A.30

B.42

C.none of these

D.84

Answer 1

42

Explanation:

The correct choice is marked.

If you follow instructions, you will compute the quotient for each value in the set:

2520 ÷ 30 = 84

2520 ÷ 42 = 60 . . . . . the value we're looking for (we need go no further)

2520 ÷ 84 = 30

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The easier way to solve the problem is to multiply the equation by x/60, so you have ...

2520 ÷ 60 = x

Then, you're doing one division instead of two or three.

2520 ÷ 60 = 42 = x