<h3>
Answer: 62</h3>
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Explanation:
18 people get off, and 21 get on
We can write the 18 as -18 to indicate a loss of 18 people. The 21 as +21 to mean we gained 21 people.
The net change is -18+21 = +3 or simply 3.
After the first stop, 3 more people are on the train compared to before reaching this stop.
If x is the number of people before the stop, then x+3 is the number of people after the stop. Set this equal to 65 and solve for x.
x+3 = 65
x = 65-3
x = 62 people were on the train to begin with.
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Check:
62 people to start off
62-18 = 44 people after the 18 people get off
44+21 = 65 people after the 21 new people get on
The answer is confirmed.
. To find the lateral area you shoul multiply this with it's height. So, 
(h is height).