Answer
The area of the platform :
56 = (3x+2) × x
Explanation (+ solving for x)
Let the width of Rectangular Platform is x feet.
Then,
Length of Rectangular Platform is (3x+2) feet
Area of Rectangular Platform = Length × width

Since x can't be negative,
Value of x is 4 feet.
So, width of Platform= 4
feet Length of Platform = 14 feet