Answer:
300
Step-by-step explanation:
Let x represent the number of adults in the zoo at 12 pm. Then the number of children at that time is 855 -x.
The number of remaining children is 1/5 of the number at 12 pm, so is ...
(855 -x)/5
The number of remaining adults is 1/4 of the number at 12 pm, so is ...
x/4
There are 36 more remaining children, so we have ...
(855 -x)/5 -x/4 = 36
171 -9x/20 = 36 . . . . . collect terms
135 = 9x/20 . . . . . . . . add (9/20)x-36
(20/9)(135) = x = 300 . . . . . multiply by 20/9
There were 300 adults in the zoo at 12 pm.
