You have done the first step successfully: multiplying the first equation by 4 gives you 1.2x - 0.8y =16, and multiplying the second equation by 3 gives you 1.2x + 0.9y = -3.

Now, apply the elimination method. I'm not sure where you got the result you have. If you are having trouble understanding the elimination method, try Googling for "solve equations by elimination"