Simplify each expression (prerequisite skill)
A. 3x - 5 - x
B. 4x - 5y + x + 7y
C. 6-7y - 1 - 10y
D. 4(3x - y) - 2(5x + 6y)
E. 5x – (3x – 9y) + y
F. 2(4x - 6 - 7 - 8) + 3(x - 2y)
(9x – 6y) – (9x – 6y)

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?