The regular price of a child's entry ticket to a water park is $6 less than that for an adult's. the park offers half off all entry tickets during the off-peak season. the sandlers paid a total of $78 for 1 adult ticket and 2 child's tickets to the water park during the off-peak season. the following equation represents this situation, where x represents the regular price of an adult ticket:
78 = 1/2x + (x − 6)
what is the regular price of a child's ticket?
$50
$56
$75
$81

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?