Discrete math

which of the following functions f : {0, 1, 2, 3} ! {0, 1, 2, 3} are onto?
1) f(x) = x
2) f(x) = x^2 mod 4
3) f(x) = x^2 - x mod 4

4) f(0) = 3, f(1) = 2, f(2) = 1, f(3) = 0
5) f(0) = 1, f(1) = 2, f(2) = 1, f(3) = 2

Asmall foreign car gete 42 miles per gallon and user 35 gallons on a trip.gasoline costs $1.05 per gallon.what was the cost of gasoline per mile driver?

Phyllis and chen are saving money to go to a football game. each friend starts with some money and saves a specific amount each week. phyllis made a graph to show the total she has saved at the end of each week. chen wrote an equation to show the total, y, he has saved at the end of each week, x. y = 15x + 15 compare the amount that each friend has when both friends start saving. select the correct answer from the drop-down menu to complete the statement. phyllis starts with $ and chen starts with $

At a kentucky friend chicken, a survey showed 2/3 of all people preferred skinless chicken over the regular chicken. if 2,400 people responded to the survey, how many people preferred regular chicken?