This is true. The closer to the mean that a value is, the more likely it is to occur.
In this case, two and three standard deviations away are both fairly unlikely, however, two is still more likely to occur than three.
Step-by-step explanation:
9 + y^2 = 49
y^2 = 40
y = √40 = 2√10
4.5/3 = 2√10/5x
22.5x = (3) 2√10
22.5x = 6√10
x = 6√10/22.5 = 3√10/11.5
140 pages
1/3 of 300 is 100pages
20% of 200 (remaining pages) is 40
100 + 40 = 140