Assuming that x represents the length of the rope that is not touching the pole, we can use the Pythagorean theorem to find the length of the rope that is touching the pole. If we let y be the length of the rope that is touching the pole, then we have:
y^2 + 4^2 = 5^2
Simplifying this equation, we get:
y^2 + 16 = 25
Subtracting 16 from both sides, we get:
y^2 = 9
Taking the square root of both sides, we get:
y = 3
Therefore, the length of the rope that is not touching the pole is:
x = 5 - y = 5 - 3 = 2
So the equation that Greg can use to find the value of x is:
x = 5 - y
where y is the length of the rope that is touching the pole, which can be found using the Pythagorean theorem.