Alright so f(x) is a fancy way of saying "y", kinda. it's asking for f(2), and since 2 is in the x spot, you can assume that x is equal to 2. You can now plug 2 into the variable x.
so now it looks like (2+1)²
Follow order of operations, PEMDAS,
Parentheses come before exponents, so add 2 and 1 together, which hopefully you already know is 3.
now you have (3)²
this can be read as 3 to the power of two, or three squared. this means that you multiply 3 by itself.
this gives you 9 as f(2),
a.9
(x+1)²
plug in