Expression 3, because 6 and 8 are factors of 48. Since positive 6 & 8 are the two numbers of choice, the product will be positive. My answer is reasonable because if you were to multiply positive 8 and 6 you will get positive 48.
Referencing off of line t being a straight line, a straight line is 180 degrees. If you subtract 108 from 180, you would get 72. Since this intersecting line is going through 2 paralel lines, the 2 groupings of angles reflect each other.