Question

Вычисли удобным способом
2+9+8=
3+8+7=
2+10+8=

Answer 1

Решение:
$2 + 9 + 8 = (8 + 2) + 9 = 10 + 9 = 19 \\ 3 + 8 + 7 = (3 + 7) + 8 = 10 + 8 = 18 \\ 2 + 10 + 8 = (2 + 8) + 2 = 10 + 10 = 20$