multiply the first equation by 5
20x -15y = -200
multiply the second equation by 3
27x +15y =12
add the 2 new equations
20x-15y +27x +15y = -200 +12
47x = -188 (devide each side by 47)
x = -4
substitute x with -4 in any equation you like (I'll choose the second)
9*(-4) +5y =4
-36+5y=4 (add 36 to each side)
5y= 40
y= 8
