How do I solve a simultaneous equation in two variables when they have with different coefficients?

First have a look at the coefficients of each variable. You're trying to spot if the coefficient of one variable is a multiple of the coefficient of the other in the second equation. If so, you can multiply either equation so you have the same term in each. Then you're able to cancel out the variable be either substituting, adding or subtracting the equations. This leaves you with one variable to find- which you can then substitute in to one of your original equations to find the other.
If neither coefficient is a multiple of the other, you find the lowest common multiple of the coefficients in order to get the same term in both equations. Then you go ahead and cancel it out.