i can't solve the equation using matrix

Question

here is the problem  

 

3x + 4y = 12

2x + y  = 13

 

i need help step by step in how to solve this problem using matrix 

Answer 1

... Or to avoid fractions:

 

| 3  4   12 |

| 2  1`  13|

 

-R2 + R1 ->  | 1  3  -1 |

                   |  2  1  13 |

 

-2R1 + R2 ->  | 1    3   -1  |   -(1/5)R2  -> | 1  3   -1 |   -3R2 +  R1   | 1  0  8  |    x = 8, y = -3

                     |  0  -5    15 |                     | 0  1  -3  |                      | 0  1  -3 |

 

 

Answer 2

3  4   |   12

 

2   1 |    13

 

divide R1 by 3 -----> R1

 

1 4/3   | 4

2   1  | 13

 

R1 - .5 R2   ---> R2

 

1   4/3   | 4

 

0   5/6   |  -5/2

 

multipy R2 by 6/5

 

1   4/3   | 4

0    1     |  -3

 

R1 - 4/3 R2 ----->  R1

 

1 0 |  8

0  1 | -3

 

x = 8, y = -3