How do you know a number is divisible by 5?

Jack did 3/5 of all problems on his weekend homework before sunday. on sunday he solved 1/3 of what was left and the last 4 problems. how many problems were assigned for the weekend?

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 it's length. what is the length of louis's basement

Which of the following functions corresponds to the above sinusoid? a. 10 cos πx - 5 b. -5 sin x - 5 c. -10 cos πx/2 - 0.5 d. 10 sin πx - 5