PLEASE HELP ME ASAP! Tony paints 21 square feet in 10 minutes.

A. What Fraction represents his constant rate, C?

B. What fraction represents his constant rate c, if it takes him x minutes to paint 84 square feet.

C. Write and solve a proportion using the fractions from parts (a) and (b) to determine how much time it takes him to pain 84 square feet.

D. Write a two-variable equation to represent how many square feet Tony can paint over any time interval.

PLEASE HELP ME ASAP!

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?