Problem of the week

GOING NUTS
Chip and Dale separated the peanuts they had collected into two piles. One pile was for doubles (shells with two peanuts inside), and the other for triples (shells with three peanuts inside). Whey they had finished shelling the peanuts, Chip and Dale had 35 shells and 78 peanuts.
How many shells were doubles and triples?

Remember to include:
• Solution
• Strategy
• proof