ANSWERS
a. A(10) = 10
b. A(0) = 0
c. A(-3) = 3
d. A(3.14159) = 3.14159
e. x = 7, x = -7
f. A(x) = -5 is not from this function
Step-by-step explanation
To find the answers to a to d we just have to write the number that inside the parenthesis as a positive number if it's negative.
For e the result is positive, so x can be either positive or negative:

Result f does not belong to this function, because the function is always positive. If x is positive, then the value of the function is the same value of x. If x is negative, the value of the function is -x, hence this value is positive too.