Question

Solve x/5 - x/2 =21. What is the value of x?
A.-70
B.-7
C.7
D.70

Answer 1

A. -70

Explanation:

Answer 2

`(x)/(5) - (x)/(2) = 21`

We need a common denominator to subtract. Easiest way to do this is to find the LCM for both denominators. The number 10 will work since both 5 and 2 are multiples of 10 and 10 is LCM is 10 and 2.

`(x)/(5) - (x)/(2) = 21` =>

`(2x)/(10) - (5x)/(10) = 21`

Subtract normally.

`(2x)/(10) - (5x)/(10) = 21` =>

`(-3x)/(10) = 21`

Multiply each side by 10

`(-3x)/(10) = 21` =>

`-3x = 210`

Divide both sides by -3

`-3x = 210` =>

x = -70

The correct answer is A.