"how many 5-card hands have a single pair and no 3-of-a-kind or 4-of-a-kind? "

How to do this , and can some one explain

Boris needs to buy plastic spoons. brand a has a box 42 spoons for $2.37. brand b has a box of 72 spoons for $3.57. find the unit price for each brand. then state which brand is the better buy based on the unit price. round your answer to the nearest cent.

F(x) = 1/x g(x)=x-4 can you evaluate (g*f)(0) ? why or why not?