8a + 12b = 92
6a – 4b = 4

a  =  4

b  =  5

Step by Step:

Solve for  

a in the first equation.

a = 23 −3b

      2     2

6a − 4b = 4

Replace all occurrences of  a in 6a − 4b = 4 with

23 −3b  

 2    2

a = 23  − 3b

     2       2

6 ( 23 − 3b ) − 4b = 4

      2      2

Simplify  6 ( 23 − 3b )− 4b

                     2     2

a = 23 − 3b  

        2     2

69 − 13b = 4

Solve for b in the second equation.

a = 23 −3b

     2     2

b = 5

Replace all occurrences of b in a = 23 −3b with 5

                                                              2    2

a = 23 − 3(5)

     2        2

b = 5

Simplify

23 − 3(5)

2        2

a = 4

b = 5

it would be 6xy and -16xy.