Pls help with 15 and 18( ignore the b it’s for another problem) pls show how you set up the problems

Find the value of ax 4 ; a = 2, x = 1. select one: a. 2 b. 4 c. 1 d. 8

Question 13 (1 point) jerome is starting a new job. his contract states he will earn $42,000 the first year, and will get a 4% raise per year. which function s(x) represents jerome's salary after a certain number of years, x?

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?