To evaluate a function, or find a functional value, means to substitute a given value in the domain into the equation to find the corresponding element in the range.
Use the function f(x)=3x1 to find f(2)
To evaluate expressions with absolute value symbols, first simplify the quantity inside the absolute value symbols and take the absolute value. Then perform any other operations.
Plug x=2 into the function and simplify.
f(x) 
= 
3x1 

f(2) 
= 
321 
Plug in x=2 
f(2) 
= 
31 
Subtract 
f(2) 
= 
3(1) 
Take the absolute value 
f(2) 
= 
3 
Multiply 