How do you get P=12.4-4Qd to equal P=-2.6+2Qs? You have to find the equalibrium so you have to set Qd=Qs so I can't figure out how to get p in the equations and the equations to equal Qd & Qs.

Answer 1

At equilibrium, Pd (price demand) = Ps (price supply), and that Qd=Qs. So,
12.4-4Q=-2.6+2Q. Solve for Q:
15.0-4Q= 2Q
15.0 = 6Q
(15/6) = Q

Answer 2

2.5