How can i group these numbers 15 divide 3x5+4x8 to equal 40

Mary used 1/7 of a spool of ribbon to complete 4 projects. she used the same amount of ribbon on each project. how much ribbon did she use on each project?

Trish receives $450 on the first of each month. josh receives $450 on the last day of each month. both trish and josh will receive payments for next four years. at a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments?

Jane moves from a house with 71 square feet of closet space to an apartment with 45.44 square feet of closet space. what is the percentage decrease of jane’s closet space?