Hey there :)
We know that the area formula of a rectangle is:
Area = width x length
The given are :
Width = p
Length = 5 + p
Area = 104 ft²
Let us substitute and find p
104 = ( p ) ( 5 + p )
104 = 5p + p²
p² + 5p - 104 = 0
Factor it
Product = - 104 and Sum = 5
Factors = - 8 and 13
( p + 13 )( p - 8 ) = 0
p = -13 p = 8
↓
We reject the negative value since a side can never be negative
Therefore,
Width = p = 8 ft
Length = 5 + p = 5 + 8 = 13 ft