from the following two equations: 3a-2b=11 5a+7b=39 find a and b

Question

please show me step by step on how to solve it

Answer 1

1. You need to eliminate one of the variables so multiply the first equation by (-5) and the second equation by (3). So you get:

 

-15a + 10b = -55

 

15a + 21b = 117

 

2. The a term can now be cancelled out and the rest of the terms are added together leaving you with:

 

31b = 62

 

3. Now solve for b by dividing both sides by 31.

 

b = 2

 

4. Now plug in the value for b into one of the original equations:

 

3a -2(2) = 11

 

5. Now solve for a

 

3a - 4 = 11

3a = 15

a = 5