Can somebody pl me with this problem

If n stands for number sold and c stands for cost per item, in which column would you use the formula: ? a. column d c. column f b. column e d. column g

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document

Susie wants to take her friend out for lunch.she wants to spend $9.75 each person. how much will she spend in all.