Julie drives 100 mi to grandmothers house on the way to

Question

Solve the all parts of following problem:

Problem: Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 50.0mph and half the distance at 77 mph. On her return trip, she drives half the timeat 50.0mph and half the time at 77 mph.

Part I: What is Julie's average speed on the way to Grandmother's house?

Part II: What is her average speed on the return trip?

I need help to determine her average speed on the return trip.