Let's find out the area of the two parts separately to see which part is smaller.
Area of rectangle is given by Length * Width
Area of Part 1
Width of Part 1 is 16'
Length of Part 1 is 16-12 = 4'
So area of Part 1 is 16*4 = 64' square
Area of Part 2
Width of Part 2 is 8'
Length of Part 2 is 8'
So area of Part 2 is 8*8 = 64' square
So area of both the parts is same . Hence Jeremy may choose any of the parts.
Hope it helps ..!!