Adding to 8 and 7

8 needs 2 to make 10. So for any 8+ problem, break off 2 from the other number. 8+3: break 3 into 2+1, make 10, then 10+1=11. 8+5: break 5 into 2+3, make 10, then 10+3=13. 8+7: break 7 into 2+5, make 10, then 10+5=15. Always take 2 from the partner.