Candace asked 100 students which crisp flavour they liked best out of ready salted, cheese and onion or salt and vinegar.
42 of the students are boys.
17 of these boys liked cheese and onion the best.
15 girls liked ready salted best.
23 out of the 39 students who like salt and vinegar best are girls.
Work out the number of students who like ready salted best.

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?