Mike has already written 8 pages, and he expects to write 1 page for every additional hour spent writing. How many hours will Mike have to spend writing this week in order to have written a total of 42 pages?

$\frac{42 - 8}{1} + 8 \cdot 1 = 42$
The rest of the pages take 1 hour each to write, so the rest of the pages he has to write is $42 - 8 = 34$ hours.
Therefore, he would take in total $34 + 8 = 42$ hours to write a total of 42 pages.