To figure this out simply set the equations equal to each like this 2x - 3 = -x + 6 this works because if both of the equations are equal to y then you can simply substitute one them in for y and solve.
To check substitute 3 into the new equation and solve: 2(3) - 3 = -3 + 6 6 - 3 = -3 + 6 3 = 3
