-7x + 4y = -6
2x - 5y= 21
Make it so x's are equal
-14x + 8y = -12
-14x - 40y = 147
Subtract
-32y = -169
Divide
y = 5.28125
Plug in the y value
2x - 5(5.28125) = 21
Simplify
2x -26.40625 = 21
Add
2x = 47.40625
Divide
x = 23.703125
Hope this helps! ;)