Jawapan

2015-03-18T20:39:39+08:00
 7u-9=2u5
7u-2u=5+9
     5u=14
       u=2.8#
3 3 3
2015-03-18T21:41:00+08:00
7u - 9 = 2u x 5
7u - 9 = 10u
7u - 10u = 9
-3u = 9
u = 9/(-3)
u = -3
1 5 1