Hi there!
I am not the greatest at functions, but I hope this helps you!
Part 1:
The input is multiplied by 2 and increased by 1 to get the output.
Or, the output is all odd numbers (consecutively) and the input is all numbers both even and odd (consecutively).
Part 2:
F(n) = 2x + 1
The blank next to the input 3 would be 7 because (3 x 2) + 1. The blank next to the output 13 would be 6.