What is the surface area of a rectangular prism that has a length of 9 feet a width of 5 feet and a height of 7.5 feet

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?