Answer: Hello mate!
in the graph you can see that:
Jonathon does 2 pushups when he does 15 crunches.
then he does 4 = ( 2+ 2) pushups when he does 30 = (15 + 15) crunches
this means that he does 2 pushups more than before, and 15 crunches more than before.
and 6= (2 + 2 +2) pushups when he does 35 =(15 + 15 + 15) crunches.
this, again, means that he does 2 pushups more than before, and 15 crunches more than before.
then you can see that he does 2 pushups for every 15 crunches.