Answer:
Here is the equation:
f(r)=4r+1
You need to find f(3). To do that, substitute all the x's with 3:
f(r)=4r+1->f(3)=4x3+1
The first thing you need to do is multiply 4 by 3. Multiply:
4x3=12
Here is your new equation:
f(3)=12+1
To get your answer, you need to add 12 and 1. Add:
12+1=13
That means:
f(3)=13
If you have any questions, feel free to ask in the comments! :)
Explanation: