Solve the simultaneous equations 5x+y=21 and x-2y=9

To answer this, you need to try and remove on of the letters from the equation. You could multiply the first equation by 2 so that the number in front of the y's are the same in both equations, with 10x+2y=21. Then, if you take the 2^ndequation away from the 1^st, the y terms will disappear giving you 4x=12. Then, to get x, divide through by 4 for x=3. That’s one half of the answer, now to get y, sub x=4 into one of the equations and rearrange for y. Subbing it into the top one: 5(4) + y = 21 so 20+y=21 and y=1. So, x=4 and y=1.