Step 1
Determine number of minutes Steve walked a mile
= 27minutes/3 miles
= 9 minutes/mile
Step 2
Out of 4.5 miles, Steve has already walked 3 miles
number of miles remain = 4.5 - 3
= 1.5 miles
Step 3
Time to finish remaining mile = 1.5 x 9
= 13.5 minutes
Total time Steve will use to finish his 4.5mile = 27 minutes + 13.5 minutes
= 40.5 minutes