Question

Дополни до 20 числа: 17, 19, 18, 16, 15.

Answer 1

17+3=20; 19+1=20; 18+2=20; 16+4=20; 15+5=20

Answer 2

17, 19, 18, 16, 15, 17, 16, 18, 19, 21, 20
закономерность: +2,-1,+2,-1,+2,-1