Answer:
y = 0.25x
(0, 0) and (10, 2.5)
Explanation:
The image of line g is attached below.
Line g passes through the point (0,0) and (10, 5). The slope of line g is gotten using the formula:

Since the third turtle is going to be half as fast as the turtle on line g. Therefore the slope of the line for the third turtle is:
m = 0.5 sec/cm ÷ 2 = 0.25 sec/cm
m = 0.25 cm/sec
Also the third turtle line would pass through the point (0,0). We can get the equation of the third turtle line using:

When x = 10, y = 0.25(10) = 2.5
Two points on the third turtle line is (0, 0) and (10, 2.5)