Here is a graph with the equation you gave graphed on it.
The correct answer should be 4
hope this helped!
Well if you buy only 1 of each, it would cost you 7.85 in total. if you subtract that from 20, it equals 12.15.
you can also make it a linear equation if you want more or less than 1 fruit and or sandwich
s=sandwich
f=fruit
5.7f+2.15f=20
