Form an equation like this
x+4x+9=84 (remember the word "is" is used as an equal sign)
Simplify them
5x+9=84
5x=84-9 ----> (I transfered 9 so that we can combine like term and remember that 9 is positive at first but transfering it to the other will make its sign negative)
5/5x=75/5 ---> Divide both sides by 5
x=15 the second number
4x+9=69 the first number and that's what we're looking for.
Proof:
69+15=84
