Can someone explain two ways i can solve a logarithmic equation?

Determine the number of girls in a math class with 87 boys if there are 25 girls for every 75 boys

In the diagram, be and ad pass throughthe center of circle o, and the area ofsector aoc is 47.45 square units. what isthe area of sector boc? use the value =3.14, and round your answer to two decimalplaces.22.33 square units25.12 square units

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?