Answer:
Step-by-step explanation
Givens
Given Length: 3x - 8
Width: 7x
Area: 7x * (3x - 8) Remove the brackets
Area: 21x^2 - 56x
Now double the length
New Length = 2 * old length
old length = 3x - 8
New Length = 2(3x - 8) Remove the brackets
New Length = 6x - 16
The width remains as 7x
Area = New Length * width
Area = (6x - 16)*7x Remove the brackets
Area = 42x^2 - 112x
Observe
42x^2 is twice as big as 21x^2
-112x is twice as small as 56x
So the area has changed by a factor 2
