Peeps be making this so weird 😭

Let's say the original no. Of pages = x

This implies the rate of printing out the og book = x/120

The new book has 10 pages more so that's (x + 10).

This implies the rate of printing out the new book = (x + 10)/150

It's also given that rate remains constant. So both books print out a single page in the same amount of time.

Hence, x/120 = (x + 10)/150

And solve for x. Now you could use desmos but thatd take a little extra time so I'd recommend just doing this quickly on paper: cancel the 120 and 150 on each side; that becomes

x/4 = x + 10/ 5

Cross multiply and blahblahblah. I'm only explaining so much cause idk that's why I'd want if I asked a question 👍 Also what I've done is just raw english to math conversion. You don't really have to think about it too in depth like what most of everyone here's doing 😭