Answer:
25 pages
Step-by-step explanation:
To start, you need to subtract the pages he's already read.
420 - 45 = 375
He'd have 375 pages left to read
If you equally distribute the number of pages left (375) by the number of days (15) you come across this:
375 ÷ 15 = 25
He'd have to read 25 pages a day.
