Answer: 12x^2 + 26x - 16 (choice D)
Work Shown
(3x+8)(4x-2)
y(4x-2) .......... let y = 3x+8
4xy - 2y
4x( y ) - 2( y )
4x( 3x+8 ) - 2( 3x+8 ) ..... plug in y = 3x+8
4x(3x) + 4x(8) - 2(3x) - 2(8)
12x^2 + 32x - 6x - 16
12x^2 + 26x - 16
This matches with choice D
I used GeoGebra to confirm the answer. WolframAlpha is another option you could use. There are many others.