I need help! what is m

Solve the system of equations using the substitution method. {y=−3x+7x=−2y−16 enter your answers in the boxes.

The mass of a marine organism, in pounds, p years after it is born is given by the polynomial function r(p) = -4p2 + 300p. find the mass when p = 20 years.

If it 8 inch candle burns at 7/10 inch per hour and a 6 inch candle burns at 1/5 inch per hour after how many hours would both candles be the same height