Ablogger who is just starting out made three videos. so far, she has 312 subscribers, who watched one, two, or all three videos. the three videos got 740 total views all together. assuming each subscriber only viewed a particular video once, how many more people watched all three videos than only one video?

Let a, b, c signify the numbers of subscribers who watched 1, 2, and 3 videos, respectively. So we can say that:

a +b +c = 312 this means that there are 312 subscribers, total

a +2b +3c = 740 this means that there were 740 total views

Next, deduct the double the first equation from the second.
(a +2b +3c) -2(a +b +c)
= (740) -2(312)
this will give us: c -a = 740 -624 = 116
Therefore, 116 more people watched all three videos than watched one video.