✔ 最佳答案
1. a × ( 1 + 5％ ) ﹦298.2 298.2 - a ﹦ ___
a x 105% = 298.2
a x 105/100 = 298.2
a = 298.2 x 20/21
a = 14.2 x 20
a = 284
∴ 298.2 - a ﹦ 298.2-284 =14.2
2. a × ( 1 + 15％ ) ﹦5175
a x 115% = 5175
a x 115/ 100 = 5175
a = 5175 x 20/23
a = 225 x 20
a = 4500
3. a × ( 1 - 70％ ) ﹦120
a x 30% = 120
a x 3/10 = 120
a = 120 x 10/3
a = 40 x 10
a = 40
4. a/2+ 150 ﹦600
a/2 = 450
a = 450 x 2
a = 900
5. a × 3/5 ﹦18
a = 18 x 5/3
a = 6 x 5
a = 30
6. 2a - 4.2 ﹦0.4
2a= 0.4 + 4.2
a=4.6/2
a=2.3
7. a × ( 1 – 3/8 ) ﹦100
a x 5/8 = 100
a = 100 x 8/5
a = 20 x 8
a = 20
8. a×( 1 + 50％ ) ﹦96
a x 150%= 96
a x 3/2 = 96
a = 96 x 2/3
a = 32 x 2
a = 64
