What is f(3)?

f(a) means the value of f(x) is ... when x = a. That means if we substitute x = 3, we would get f(3).

f(3) also means the value of f(x) is ... when x = 3.

f(x) can also be defined as y // f(x) = y

You can find the value of f(x) at specific domain from the graph by looking at x = 3 then look up to where the point or where the graph passes. From the graph, when x = 3 as we look up and the graph passes y-coordinate at 1.

Therefore we can say that when x = 3, y = 1.

f(3) = 1