How can you make a high estimate for the sum of two fractions in a world problem?

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.

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?

Point a is at 12, and point d is at 56. point c is midway between a and d, and point b is midway between a and c. which of these is the coordinate of b?