1. 直接写出得数。
$3.1 + 1.9 =$ $4.2 - 0.5 =$ $2.7 + 9.9 =$
$5.8 - 2.6 =$ $7.07 + 5 =$ $6.12 + 0.88 =$
$560 ÷ 4 =$ $0.23 × 40 =$ $2.7 × 0.3 =$
$3 ÷ 100 =$ $9 × 0.5 =$ $2.6 × 3 =$
$3.6 + 6.4 =$ $1.25 × 8 =$ $0.2 × 0.4 =$
$100 - 35.2 =$ $8.06 - 6.96 =$ $3.5 - 2.54 =$

3.1 + 1.9 = 5 4.2 - 0.5 = 3.7 2.7 + 9.9 = 12.6
5.8 - 2.6 = 3.2 7.07 + 5 = 12.07 6.12 + 0.88 = 7
560 ÷ 4 = 140 0.23 × 40 = 9.2 2.7 × 0.3 = 0.81
3 ÷ 100 = 0.03 9 × 0.5 = 4.5 2.6 × 3 = 7.8
3.6 + 6.4 = 10 1.25 × 8 = 10 0.2 × 0.4 = 0.08
100 - 35.2 = 64.8 8.06 - 6.96 = 1.1 3.5 - 2.54 = 0.96

2. 解方程。
$x - 18 = 57$ $1.5 × 3.2 + x = 45$
$90 + x = 210$ $x - 20 × 0.5 = 26$
$x - 4.1 = 9.7$ $x - 1.8 = 4.5$
$x - 4.5 = 1.2$ $x - 6 = 4.8$
$x - 6 × 8 = 26.8$ $200 - x = 120$

解：x - 18 = 57
x = 57 + 18
x = 75
解：1.5×3.2 + x = 45
4.8 + x = 45
x = 45 - 4.8
x = 40.2
解：90 + x = 210
x = 210 - 90
x = 120
解：x - 20×0.5 = 26
x - 10 = 26
x = 26 + 10
x = 36
解：x - 4.1 = 9.7
x = 9.7 + 4.1
x = 13.8
解：x - 1.8 = 4.5
x = 4.5 + 1.8
x = 6.3
解：x - 4.5 = 1.2
x = 1.2 + 4.5
x = 5.7
解：x - 6 = 4.8
x = 4.8 + 6
x = 10.8
解：x - 6×8 = 26.8
x - 48 = 26.8
x = 26.8 + 48
x = 74.8
解：200 - x = 120
200 - x + x = 120 + x
200 = 120 + x
x = 200 - 120
x = 80