800-100p=-100+200p
how also to graph it.
I believe you have supply and demand equations; Qd on the left, Qs on the right. Normally, we put P on the y-axis, and Q on the x-axis. So rewrite each equation in terms of P.
800 - 100P = Qd is transformed into P=8-Qd/100. Do the same for Supply. As for a graph, each equation is a simple line.