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?

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Answer 1 · 2015-10-16T13:28:26

#-18#

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((x +3) * 3)_(color(blue)("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#

#3x + 9 = 2x - 9#

#3x - 2x = -9 - 9#

#x = color(green)(-18)#