4x-2y=12

-4x-9=54

How can you order a ladder?

Equations:

4x - 2y = 12

-4x - 9y = 54

Multiple them in both sides

4x - 2y - 4x - 9y = 12 + 54

-2y - 9y = 66

-11y = 66

y = - 6

If y = - 6 then put y in first or second equation.

I put it in first equation

4x - 2. (-6) = 12

4x + 12 = 12

x = 0

Therefore

(x, y) = (0, - 6)