Question 715567
Procedure:


Eliminate a to solve for b.
The coefficients for a in both equations are the same.  Just subtract one equation from the other equation.


a + 9b = 3
-a + -4b = -(-2)
------------------
0a+5b=5
b=1


Eliminate b to solve for a
You would want to multiply, in this case, both equations to get the same coefficient on the b terms.
a + 9b = 3
a + 4b = -2    


Use 4 as a factor for the first one, and use 9 as a factor for the second one.
4(a + 9b = 3)
9(a + 4b = -2)

You obtain
4a+36b=12
9a+36b=-18


Next, subtract one equation from the other.  I will subtract the first from the second.
9a-4a+36b-36b=-18-12
5a+0=-30
5a=30
a=6  


Summary of result:  a=6 and b=1