Hey, please help me, I'm fairly confused with this question.
25 points for the correct answer.

Tomas used 3 1/3 cups of flour and now has 1 2/3cups left. which equation can he use to find f, the number of cups of flour he had to begin with? f+3 1/3=1 2/3 f-3 1/3=1 2/3 3 1/3f=1 2/3 f/3 1/3=1 2/3

Solve the following pair of equations for x and y: ax/b_ by /a= a +b; ax - by = 2ab

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?