Fun.
The point on the line nearest the origin is (6,8). That means the line from the origin to (6.8) is perpendicular to the line we seek.
The line through the origin and (6,8) is
6y = 8x
8x - 6y = 0
4x - 3y = 0
The perpendicular family swaps the coefficients on x and y, negating one. The constant is given by plugging in the point:
3x + 4y = 3(6) + 4(8) = 50
3x + 4y - 50 = 0
Choice a.