How to solve the simultaneous equation

3x+7y=26

4x+5y=13

I found:

x=-3

y=5

Explanation: I would multiply the first equation by - 4 and the second by 3 and add together the two equations (in columns):

{-12x-28y=-104

{12x+15y=39

0-13y=-65

So: y=65/13=5

Substitute back this value into the first equation:

3x+7⋅5=26

3x=26-35=-9

x=-9/3=-3