Marty read 4 times as many pages as Nelson and Jennifer COMBINED. Marty read 1,860 pages.
In total, after dividing Marty's total by 4, Jennifer and Nelson both read a total of 465 pages.
After subtracting Nelson's 240, Jennifer is then found to have read 225 pages.
B would be the best viable option, as it clearly shows that 240+?x4=1,860, which it does.
Hope this helped. Khan Academy is a great resource for any learner. :)