Algebra  2 more questions... ^^
posted by Jason .
Thank you for helping on the other problem, but could you maybe explain how I should solve these two problems?
1. In 1985, Barry was 13 years old and his father was 43. In what year will Barry's age be twofifths of his father's age?
2. The length of a certain rectangle is 20m and the length increased by 100m, the perimeter of the new rectangle would be twice the perimeter of the original rectangle. What are the dimensions of the original rectangle?
I did not get the fist problem at all, but for the 2nd problem I started by saying :
L=w+20 >>> l+w+20=P &&&
2(L+100)+2(w20)=2P
I then plugged things in... and... :(
please help.
once again,
jason.

1. Let the number of years past 1985 be x
then
13+x = 2/5(43+x)
65 + 5x = 86 + 2x
3x = 21
x = 7
so it will be in the year 1992 (1985+7)
for your #2, I think your wording is wrong, it does not match the expressions you have written
for l=w+20, I read that the length is 20 m more than its width, nowhere does it say that.
l+w+20=P ???
if that is to describe the perimeter it whould say:
2l + 2w = p
2(l+20 + 2w = p
2l + 2w + 40 = P
for 2(L+100)+2(w20)=2P where does it say the width is decreased by 20? 
The length of a certain rectangle is 20m and the length increased by 100m, the perimeter of the new rectangle would be twice the perimeter of the original rectangle. What are the dimensions of the original rectangle?
I started by saying :
L=w+20 >>> l+w+20=P &&&
2(L+100)+2(w20)=2P
I then plugged things in... and... :(
please help.
2(120) + (2W) = 2(40 + 2W)