By using the distance formula:

d² = (x₂ - x₁)² + (y₂ - y₁)²

Lets calculate distance between the points (x₁ , y₁) and (x₂ , y₂)

Here we have;

x₁ = - 6, x₂ = 0

y₂ = 8, y₂ = 0

d² = [0 – ( - 6)]² + [0 – 8]²

⇒

⇒ d = √(36 + 64)

⇒ d = √100

⇒ d = 10

So the distance between P ( - 6, 8) and origin O (0, 0) = 10