Question

John has 50 comic books and he increases his collection by 3 books per week

Answer 1

Let $x=$ the number of weeks. Then the John's collection $y$ will be $y=50+3x$ books after $x$ weeks.

$$1\ month=4\ weeks$$

$$y(4)=50+3(4)=62$$

The John's collection will be $62$ books after one month.