There are 15 students and a social studies class. two students will be selected to present their term projects today. and how many different orders given to students to be selected? a. 849 b. 105 c. 420 d. 210

Abike shop sells you a bicycle for $63 and a helmet for $21. the total cost is 150% of what the shop spent originally. how much did the shop spend originally? how much profit did the bike shop earn by selling the bicycle and helmet to you ?

Just tell me how to set up the equation.

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25