三、在$□$里填合适的数。（每题 1.5 分，共 36 分）
$□ - 1 = 40$ $30 + □ = 50$ $16 - □ = 6$
$73 - □ = 70$ $□ - 6 = 30$ $80 + □ = 89$
$18 - □ = 8$ $□ + 9 = 79$ $□ - 10 = 20$
$50 + □ = 54$ $70 - □ = 40$ $□ + 9 = 19$
$□ + 6 = 36$ $20 + □ = 28$ $65 - □ = 5$
$92 - □ = 2$ $□ - 7 = 30$ $50 + □ = 80$
$13 - □ = 9$ $□ + 8 = 38$ $72 - □ = 70$
$□ + 6 = 15$ $94 - □ = 4$ $2 + □ = 11$

三、1. 7 9 11 13
2. 40 50 60 70
3. 58 56 54 52
4. 75 70 65 60