有幾條數學唔識做20點。

1. 2/5 -8 = 9/5 +6
你個未知數呢-3-??

2. -1.6z+12.9 = 4.4+1.8z
12.9-4.4 = 1.8z+1.6z
3.4z = 8.5
z = 2.5

3. 7y-3(6-y) = 2(11-5y)
7y-18+3y = 22-10y
10y-18 = 22-10y
10y+10y = 22+18
20y = 40
y = 2

4. 3[6p-(21-5p)] = 4(7p - 12)
3(6p-21+5p) = 28p-48
18p-63+15p = 28p-48
18p+15p-28p = -48+63
5p = 15
p = 3

5. 6(8-2a)+22 = 3a -5(a+4)
48-12a+22 = 3a-5a-20
-12a-3a+5a = -20-48-22
-10a = -90a
a = 9

6. 2(x - 0.6)=6.2 - 0.8(x-3)
2x-1.2 = 6.2-0.8x+2.4
2x+0.8x = 6.2+2.4+1.2
2.8x = 9.8
x = 3.5

7. v+4/3 = v-1/2
會變左v-v...計到咩-3-??

8. b+3/5 + b-7/4 = 2
2b-23/20 = 2
2b = 2+23/20
2b = 63/20
b = 63/40

9. d-3/4 - d-1/6 = -1
同樣d-d -.-點計呀

10. 2x-3/4 - x-4/3 = 3/4
x = 3/4+3/4+4/3
x = 17/6

應該就冇錯架啦...
希望幫到你=]

1) 無法計算

2) -1.6z+12.9 = 4.4+1.8z
-1.6z-1.8z = 4.4-12.9
-3.4z = -8.5
z = 2.5

3) 7y-3(6-y) = 2(11-5y)
7y-18+3y = 22-10y
7y+3y+10y = 22+18
20y = 40
y = 2

4) 3[6p-(21-5p)] = 4(7p - 12)
18p-63+15p = 28p-48
18p+15p-28p = -48+63
5p = 15
p = 3

5) 6(8-2a)+22 = 3a -5(a+4)
48-12a+22 = 3a-5a-20
48+22+20 = 3a-5a+12a
90 = 10a
a = 9

6) 2(x - 0.6)=6.2 - 0.8(x-3)
2x-1.2 = 6.2-0.8x+2.4
2x+0.8x = 6.2+2.4+1.2
2.8x = 9.8
x = 3.5

7) 題目錯

8) b+3/5 + b-7/4 = 2
b+b = 2-12/20+35/20
2b = 63/20
b = 63/40

或者

b+3/5 + b-7/4 = 2
b+0.6+b-1.75 = 2
b+b = 2-0.6+1.75
2b = 3.15
b = 1.575

9) 題目錯

10) 2x-3/4 - x-4/3 = 3/4
2x-x = 9/12+9/12+16/12
x = 34/12
x = 17/6