The answer is 4 I am sure it is
If Nathan does 9 minutes of push ups for 3 days, that's 9 divided by 3, which is 3. (9/3=3) So nathan does 3 minutes of push ups each day, so just multiply each day by 3 to find the correlation between the two.
The Table should look like this:
# of days # of Minutes
1 3
2 6
3 9
4 12
5 15
6 18
7 21
Let y be the unknown number
The other number is x - 12
This is more or less how you write the question.

To solve it invert the 1/2 and multiply.

Which gives you 14 /8 whis is 1 3/4 cups.