Question 200900
Let  x=short  length,,,,y=  long  length
.
(1)  x + y = 20,,,,,y = 20 -x
(2) 4x = 3y-4
.
substitute  (1) in (2)
.
4x = 3( 20-x) -4
4x = 60 -3x -4
7x =56
x=8
.
substitute  in  (1)
.
y= 20 -8
y=12
.
check  (1) 8+12 =20,,,,ok
(2)  4(8) = 3( 12) -4
32 =32,,,,,,,,,,,,,,,,,,,,,,ok