maths..10 points!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

7u-(4u-1)/2=21
14u-(4u-1)=42
10u+1 = 42
10u = 41
u = 4.1

From what you typed here 7u-(4u-1除2)=21
I read it as 7u-(4u-0.5)=21

so it should be:
7u-4u+0.5=21
3u=21-0.5
3u=20.5
u=6.83

so pls double check your equation and make sure you get the right one...

7u-(4u-1/2)=21
7u-4u+1/2=21
3u=21-1/2
3u=42/2-1/2
3u=41/2
u=41/2*1/3
u=41/6

7u-21=4u-1除2
7u-4u=21-1除2
3u=20又2份1
3u=41/2
u=41/2 x 1/3
u=41/6
u=6 5/6 (6又6份5)