Answer:
16 km is the answer
Explanation:
a (Colton to parents' house) = 12 km
b = ?
c (parents' house to grandparents' house) = 20 km
According to the Pythagoras theorem,
a² + b² = c²
12² + b² = 20²
144 + b² = 400
b² = 400 - 144
b² = 256
b = 16
∴ Colton is 16 km away from his grandparents' house.