Question 262455
Edwin is right. Substitution is the worst way to solve it.
Elimination is the way to go.
Just so you see how much easier it is with elimination.

This system begs to be done by elimination.
9 is a multiple of 3 and 4 is a multiple of 2.
Sow e have several choices.
I choose multiply first by 3 and add
6x+9y=15
4x-9y=9
add
10x=24
x=24/10 or 12/5 or 2.4 
we could just plug 12/5 into any equation and solve for y
but we'll solve using elimination too!
multiply first equation by 2
4x+6y=10
4x-9y=9
subtract
15y=1
y=1/15

x=12/5
(12/5,1/15)
These equations were begging for elimination.