Answer
Your speed relative to the ground is 61 km/h.
Work Step by Step
This is how we add velocities that are much smaller than the speed of light. This is discussed on page 659.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.