Julie drives 90mi to grandmothers house on the way to

Question

Compute all parts of following problem given below:

Problem: Julie drives 90mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 25mph and half the distance at 65 mph. On her return trip, she drives half the time at 25mph and half the time at 65mph.

Part A: How long does it take Julie to complete the trip to Grandmother's house?

Part B: How long does the return trip take?

Explanation and formulas needed for best solution!