I just need the equation you'd plug into the quadratic formula i don't want the solutions

Ateacher has $80 to buy workbooks. each work book cost $3. if she buys as many workbooks as possible, how much money does she have leftover? a) $2 b) $4 c) $6 d) $8

Don't know how to find x given these segment lengths

Binh says the point of intersections is (0,-3) which statements identify the errors binh made , check all that apply