Răspuns:
1) (17+13)÷2=15
(23+41)÷2=31
(28+52)÷2=40
(37+33)÷2=35
2) (3+5+13)÷3=7
(6+7+11)÷3=8
(5+7+15)÷3=9
(8+9+19)÷3=13