Which expression is the best estimate of Four-fifths times 22.01?

One-fifth times 20
Four-fifths times 20
4 × 20
5 × 20

Solve each quadratic equation by factoring and using the zero product property. 14x - 49 = x^2

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?

Write 5 in the form of a/b using integers to show it as a rational number