What are the new coordinates?

For a read-a-thon, jay and odhràn each started reading a book at the same time and continued reading for several hours. jay's book had 278 pages, and he read 55 pages per hour. odhràn's book had 238 pages, and he read 45 pages per hour. after how many hours did they have the same number of pages left, and how many pages were left?

How to choose the sign of the radical in the denominator of the formula for the distance from a point to a line.

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=