Answer:
1.5, -8, 0, 2f, 2/3
Explanation:
j(x) = 2x means the function name is j, and it is a function of the variable x. To evaluate the function, you put the given value everywhere you see x, and do the arithmetic.
j(0.75) = 2(0.75) = 1.5
j(-4) = 2(-4) = -8
j(0) = 2(0) = 0
j(f) = 2f
j(1/3) = 2(1/3) = 2/3