Question

If you add 21 to my number and then multiply the result by 3, you will get 84 more than two-thirds of my number. Find my number.

Answer 1

Based on the calculations, the unknown number is equal to $\frac{-45}{7}$

• Let the unknown number be x.

How to find an unknown number:

Translate the word problem into an algebraic expression, we have;

Adding 21 to the unknown number:

$21 +x$

Multiplying the result by 3:

$3\times (21+x)$

84 more than two-thirds of the unknown number:

$\frac{2x}{3} +84$

Equating the equations, we have:

$3\times (21+x) = \frac{2x}{3} +84\\\\43+3x=\frac{2x}{3} +84$

Cross-multiplying, we have:

$43+3x=\frac{2x}{3} +84\\\\129+9x=2x+84\\\\9x-2x=84-129\\\\7x=-45\\\\x=\frac{-45}{7}$

Read more on word problems here: brainly.com/question/13170908