Question

What is the missing numerator?


`(5)/(7) + (?)/(6) = (51)/(42)`
a. 2
b. 3
c. 8
d. 10

Answer 1

3

Explanation:

As with any other addition fact problem, you can isolate the unknown term by subtracting the unwanted constant.

5/7 +x/6 = 51/42

x/6 = 51/42 -5/7 . . . . . subtract 5/7 from both sides

x/6 = 51/42 -30/42 = 21/42 = 1/2 . . . . . complete the subtraction

x = 6(1/2) = 3 . . . . . . . . multiply by 6

The missing numerator is 3.

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Alternate solution

Multiply the equation by 42:

30 +7x = 51

7x = 51 -30 = 21 . . . . . subtract 30

x = 21/7 = 3 . . . . . . . . divide by the coefficient of x