How do i solve this problem?

Use the function f(x) is graphed below. the graph of the function to find, f(6). -2 -1 1 2

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

Jacob signs up to work for 2 1/2 hours at the school carnival. if each work shift is 3/4 hour, how many shifts will jacob work? (i just want to double check : |, for anybody that responds! : )