Pleassssssssss help guys please

Answer:
Each sandwich costs $3
Step-by-step explanation:
4 pairs of socks that cost $7 is 28$, and you have to take
salim's total money (40$) minus the $28 and you get $12
take 12 and divide it by his 3 sisters and himself (4 people)
and you should get $3 for each sandwich