The answer is D.
The full specification of Newton's First Law is (from Wikipedia)
In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
On earth we're generally in slightly a non-inertial frame, with rotation and revolution around the sun. It's also impossible to turn of gravity, so objects are being acted upon by an outside force. Typically there's also the outside force of friction, which makes things tend to stop.
2 ways to find the y int.
(1) put the equation in y = mx + b form and the y int will be in the b position
7x - 3y = -5
-3y = -7x - 5
y = 7/3x + 5/3....so 5/3 is ur y int
(2) another way is to sub in 0 for x and solve for y
7(0) - 3y = -5
-3y = -5
y = -5/-3
y = 5/3...ur y int
1.25/20=1x
1.25x=20
x=20/1.25=16
1 inch=16 feet