Solve the simultaneous equations y=2x and y=x+3

As both equations have y on the left hand side we can put the right hand sides equal to each other, so 2x=x+3. We can then subtract x from both sides. This gives 2x-x on the left hand side which is x, and x+3-x on the right hand side which is eqaul to 3. If we put these into 2x=x+3 we have x=3. Now we need to find y. In the question we are given that y=2x, therefore y=2*3=6.