Solve the simultaneous equations 5x + y = 21 and x - 3y = 9

To begin with, I would begin by explaining that in a situation with simultaneous equations one of the variables must be eliminated to find the values for y and x.In this specific case I would make the x variables have the same coefficient and multiply the second equation by 5 giving 5x-13y=45The next step would be to subtract one equation from the other as so: 5x-13y=45 - 5x + y = 21 resulting in an answer of -16y=24This equation can rearrange to y= -1.5Using this value in either of the original equations you can solve for xBy using x-3y=9 and rearranging for x to give x=9+3y then substituting in the value for y to obtain x=4.5