The solution to the system of equations

Question

x+3y=12

4x-y=-17 is

Answer 1

x + 3y = 12    ---------(1)

4x - y = -17  -----------(2)

To make y-coefficients equal , multiply the equation (2)  with 3

12x - 3y = -51   -----(3)

Add equations (1) and (3)

   x + 3y = 12 

12x - 3y = -51 

-------------------

13x = -39

x = -39/13

x = -3

Now put x = -3 in equation (1)

-3 + 3y = 12

Add 3 on each side

-3 + 3y + 3 = 12 +3

3y = 15

y = 15/3

y = 5

So x = - 3 and y = 5