Help a girl out

Question

It took Debbie1.8 hours to drive to her? mother's house on Friday morning. On her return trip on Saturday night, traffic was? heavier, so the trip took her 2 hours. Her average speed on Saturday was 3 mph slower than on Friday. What was her average speed on Saturday??

Answer 1

distance=rate*time

d=rt

d=r*1.8

d=(r-3)*2

equate the two right sides

1.8r=2(r-3)

1.8r=2r-6

2r-1.8r=6

0.2r=6

2r=60

r=60/2

r=30 mph on Friday

r-3=30-3=27 mph Saturday

check:

30*1.8=54 miles

27*2=54 miles