How do you determine which place value to use when estimating products?

Which expression is equivalent to (9x - 3 1/ + 1 3/8)

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?

Set up and solve a proportion for the following application problem. if 55 pounds of grass seed cover 404 square feet, how many pounds are needed for 7272 square feet?