You have the following information:
- Two-thirds (which means 2/3) of the people on a hike are adults.
- There are 36 adults
In order to calculate the number of people, you consider that 36 is 2/3 of the total people. If you name x as the total people, the number of adults is 2/3x. Thus, you can write the following algebriac expression:
2/3 x = 36
you solve the previoues equation for x. First, you multiply both sides by 3 and you divide both sides by 2.
x = 36(3/2) = 108/2 = 54
Hence, the number of people on the hike is 54