一、我会计算。
$17 - 9 = $ $9 + 8 = $ $13 - 9 = $ $6 + 8 - 9 = $
$16 - 9 = $ $11 - 9 = $ $19 - 6 = $ $18 - 9 + 6 = $
$12 - 9 = $ $9 + 7 = $ $18 - 4 = $ $15 - 9 + 8 = $
$4 + 12 = $ $5 + 9 = $ $3 + 13 = $ $5 + 6 - 9 = $

8 17 4 5 7 2 13 15 3 16 14 14 16 14 16 2

二、圈一圈,算一算。
1.
$14 - 8 = □$
想：$10 - 8 = 2$ $2 + □ = □$ 或 $8 + □ = 14$ $14 - 8 = □$
2.
$11 - 8 = □$
想：$10 - 8 = 2$ $2 + □ = □$ 或 $8 + □ = 11$ $11 - 8 = □$

1. 6 4 6 6 6

2. 3 1 3 3 3