F.2 maths

第一條唔得
5x/6 = 7x/8
(5x)(8) = (7x)(6)
40x = 42x

無得計啦...解唔到

第二條有得解
x/4 -2 = x/3
x/4-x/3 = 2 通分母
(3x+4x)/12 = 2
7x = (2)(12)
7x = 24
x = 24/7 可以用假分數或者帶分數

第三條都有得解
1+x/2 + 1-x/3 = x-1/2
x/2-x/3-x = -1/2-1-1 通分母
(3x-2x-6x)/6 = -5/2
-5x = (-5/2)(6)
-5x = -15
x = (-15)/(-5)
x = 3

I wnat to say on Question 1, X = 0 is the answer.
For question 4. If you consider complex number, then all equation should have solution.

1) 5x/6 = 7x/8
40x = 42x
40=42
方程沒有解

2) x/4-2 = x/3
x/4-x/3 = 2
3x/12 - 4x/12 = 2
-x/12=2
-x=24
x = -24

3) 1+x/2+1-x/3 = x-1/2
x/2-x/3-x = -1/2-1-1
3x/6-2x/6-6x/6 = -1/2-2/2-2/2
-5x/6 = -5/2
x = -5/2 x (-6/5)
x = 3