Please help! I dont want to fail if you could do these three I will mark you as brainlest. thank you ♡

Given that de, df, and ef are midsegments of △abc, and de=3.2 feet, ef=4 feet, and df=2.4 feet, the perimeter of △abc is .

Evaluate the expression for the given value of the variable 7a - 4a for a =8

Louis wants to carpet the rectangular floor of his basement the basement has an area of 864 square feet the width of the basement is 2/3 its length what is the length of lewis's basement