一、口算。
$35 + 5 =$ $6 + 57 =$ $62 - 30 + 9 =$
$95 - 80 =$ $44 - 5 =$ $8 + 53 + 30 =$
$20 + 48 =$ $35 + 20 =$ $85 + 6 - 40 =$
$71 - 3 =$ $26 - 8 =$ $50 - 3 - 9 =$
$20 + 75 =$ $38 - 20 =$ $27 + 3 + 41 =$
$68 - 30 =$ $63 + 8 =$ $72 + 20 - 8 =$
$6 + 36 =$ $30 - 8 =$ $54 - 5 - 30 =$
$44 - 40 =$ $79 + 20 =$ $35 - 6 + 50 =$
$3 + 37 =$ $55 - 5 =$ $20 + 36 - 8 =$
$62 - 40 =$ $67 + 8 =$ $80 - 5 + 4 =$

一、40 63 41
15 39 91
68 55 51
68 18 38
95 18 71
38 71 84
42 22 19
4 99 79
40 50 48
22 75 79

二、想一想，在每个算式的括号里填相同的数。
$17 - (\quad) = 9 + (\quad)$ $29 - (\quad) = 13 + (\quad)$
$11 + (\quad) = 25 - (\quad)$ $20 + (\quad) = 36 - (\quad)$
$35 + (\quad) = 35 - (\quad)$ $30 + (\quad) = 50 - (\quad)$

二、4 4 8 8
7 7 8 8
0 0 10 10