Answer:
y = -1/2 x + 25
The relationship is linear, but it takes some doing.
Explanation:
Remark
This is a very interesting problem. I've never seen one quite like it. There is probably a much better way of solving it, but I did not discover it.
You have to introduce another variable which I labeled as z.
Let time = x
Let distance = y
Let the step away from the starting point = z which will be the same for x and y. So 18 and 16 the step away from the start is 3.
So as the time increases, the distance decreases. What we are going to do sort of resembles a parametric relationship.
t starts with 10
x = 10 + 4*(z - 1) and increases by 4 with each step
d starts with 20 and decreases by 2 with each step
y = 20 - (z - 1)*2
Now solve for z in each of the forgoing equations.
x = 10 + 4z - 4
x = 6 + 4z
x - 6 = 4z
(x - 6)/4 = z
y = 20 - 2z + 2
y = 22 - 2z
y - 22 = - 2z
(y - 22)/-2 = z
Since the zs must be kept the same, the left sides are equated
(x - 6)/4 = (y - 22)/-2 Cross multiply
-2(x - 6) = 4(y - 22) Remove the brackets.
-2x + 12 = 4y - 88 add 88 to both sides.
-2x + 100 = 4y Switch the sides
4y = - 2x + 100 Divide by 4
y = -1/2 x + 25
Now for sure you have to try this.
Let x = 14
y = -1/2 * 14 + 25
y = -7 + 25
y = 18
Try another one
Let x = 22
y = -1/2 * 22 + 25
y = - 11 + 25
y = 14
Those two at least check.