# If the sum of a number and three is tripled, the result is nine less than twice the number, how do you find the number?

Oct 16, 2015

$- 18$

#### Explanation:

Let's call $x$ the number.

You know that if you triple the sum of $x$ and $3$, you get a value that is $9$ less than twice the number $x$.

This means that you can write

${\underbrace{\left(x + 3\right) \cdot 3}}_{\textcolor{b l u e}{\text{three times the sum of x and 3")) = overbrace(2 * x - 9)^(color(red)("9 less than twice the value of x}}}$

Rearrange the above equation to solve for $x$

$3 x + 9 = 2 x - 9$

$3 x - 2 x = - 9 - 9$

$x = \textcolor{g r e e n}{- 18}$