Heather has to solve this system of equations using elimination. what should be her first step? a. isolate the x in the second equation so that she can substitute into the first equationb. solve both equations for y so that she can easily graph the equations and find the point of intersectionc. multiply the second equatuon by 3 so that the x's have the same coefficient to then add the two equations togetherd. multiply the second equation by -3 so that the x's have the opposite coefficients to then add the two equations together