Question

You travel and average speed of 20 km/h in a straight line to get to your grandmothers house. It takes you three hours to get to her house. How far is her house from where you started?

Answer 1

$20\,\dfrac{\mathrm{km}}{\mathrm h}=\dfrac x{3\,\mathrm h}\implies x=60\,\mathrm{km}$