Answer:
For every 20 minutes read each night , maths fact practiced by Preston each night=5 Minutes
Now, Maths facts practiced by Preston =45 Minutes
⇒45 minutes=5 Minutes × 9
Number of Minute read by Preston is Directly proportional to Number of minutes he practices his maths facts.
Number of Minutes read by Preston in same time period=20 minutes ×9
=180 minutes
=3 Hours
You can solve it by concept of Proportion.
