Solve the simultaneous equation: 2x - 5y = 9 , x + 6y = -4

First multiply the second equation by 2, so it becomes 2x + 12y = -8. Then subtract the second equation from the first one which gives (2x - 2x) + (-5y - 12y) = (9 - -8), -17y = 17. Therefore y = -1. Plug the y value into either the first or second equation which can then be solved to give the x value (e.g. 2x - 5(-1) = 9, 2x = 4, x = 2). The reason why you need to multiply the second equation by 2 is so that when you subtract it from the first equation, the x term can disappear making it easier to find the y value. (Note: One could also multiply the first equation by 6 and the second equation by 5 and add them together to isolate the x term instead and eliminate the y term, however this is longer and more complicated).