Please help me. I do not understand this at all

What are two numbers that have a sum of 15?

Which graph represents the function f(x)=4[x]?

What is the volume of a cardboard box that measures 1 inch by 5 inches by 7 inches? the volume of the cardboard is cubic inches. enter your answer as the number that correctly fills in the blank in the previous sentence. if necessary, round your answer to the nearest tenth, like this: 42.5