Answer:
x=2
Step-by-step explanation:
3^2x = 81
3^2x = 3^4
Compare powers
2x = 4
x = 2
Set up a proportion:

=

To solve cross multiply:
3000x=300000
divide both sides by 3000:
3000x/3000=300000/3000
x=100
It will take her 100 hours to drive 4000 miles assuming she continues to travel at this rate.