<PRE><B>Question 121488</B>
Let the denote length by L and Width by W

L:W=5:4.......(1)

New dimensions after length is increased by 8 and width halved
L+8:1/2W=7:2........equation (2)

Solve the two equations

L/W=5/4...multiply both sides by W 

L=5/4W

L+8/1/2W=7/2....cross multiply

2(L+8)=7/2W...open parenthesis
2L+16=7/2W

Substitute 5/4W for L
2(5/4W)+16=7/2W
5/2W+16=7/2W...like terms together
7/2W-5/2W=16
2W/2=16..Divide by 2 on both sides
W=16
L=5/4W=5/4times16=20</PRE>