15.

Find the slope of a line perpendicular to 2y=-6x+8

2/3

6

1/3

-3/2

The slope of the given line is found from the coefficient of x after dividing the equation by 2.

... y = - 3x + 4

The given line has slope - 3.

A perpendicular line will have a slope that is the negative reciprocal of this:

... - 1 / (-3) = 1/3

This corresponds to your 3rd choice.