5 Write an equation
and solve for the
variable.
12
7 7 7
a
Choose the correct equation below.
O A. a-3-15 = 7+7+7
OB. 5 + a +12= 7+ 7 + 7
O C. 12-a + 3 = 7 + 7 + 7
OD. 5 + 12 + 7 + 7 + 7 = a

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?