so convert to inprompery fractions
3 and 7/8=3+7/8=24/8+7/8=31/8
1 and 5/8=1+5/8=8/8+5/8=13/8
so each uses 1/4 cup
1/4=2/8
so
find the difference between 31/8 and 13/8
[tex] \frac{31}{8}-\frac{13}{8} [/tex] = [tex] \frac{18}{8} [/tex]
so find how many 2/8 goes into 18/8
2/8 times what=18/8
multily both sides by 8/2 to clear faction
what=144/16=36/4=9/1=9
I made 9 sandwitches