Mary drove to Birmingham Airport at 45 miles per hour for the first two hours and then at 70 miles per hour for the remainder of the journey. Her average speed for the entire journey was 60 miles per hour. How long did Mary's journey to Birmingham Airport take?

THE AVERAGE SPEED IS SET TO CONFUSE YOU.

Step-by-step explanation:

IF YOU SEE, THE AVERAGE SPEED YOU TAKE OUT WITH THE SPEEDS

INITIAL AND FINAL YOU ALREADY HAVE

v s (45 mi/h + 70 mi/h)/2 x 57.5 mi/h

ALMOST IS EQUAL TO 60 mi/h

AS FOR TOTAL TIME DISTANCE IS REQUIRED, WE KNOW  THAT MARY

TRAVELS FOR MORE THAN TWO HOURS, BUT WE DON'T KNOW  FROM

HOW FAR FROM THE AIRPORT MARY START DRIVING.  IT WON'T

TAKE THE SAME IF MARY DRIVES FROM MONTGOMERYI OR FROM

BUENOS AIRES, ARGENTINA.