1         x          x        1
----   -  ----   =   ----  -  ----
4        2           4       8

全式同乘以8化成整數便於計算→2-4x=2x-1→6x=3→x=1/2

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

全式同乘以6化成整數便於計算→9(x+1)-5=-2(x-2)→9x+9-5=-2x+4→11x=0→x=0

5 times a number is greater than 3 times the number by 4. Find the number.
Solution: Let x be the number→5x=3x+4→2x=4→x=2

The length of a rectangle is 3 cm longer than its width.The perimeter of the rectangle is 30 cm.Find the length ofthe rectangle.
設長為x, 寬為x-3, 邊長為2*(x+x-3)=30→4x-6=30→4x=36→x=9

For a product, its marked price=$50, cost price=$40 and selling price=$36.
What percentage is the price marked up?

(50-40)/40*100%=10/40*100%=25% (唔確定...)