<human>:  A fifth-grade class went on a field trip to the zoo, and their class of 10 students merged with another class with the same amount of students. 5 parents offered to be a chaperone, and 2 of the teachers from both classes will be there too. When the school day was over, the students could choose to go home and 10 of them left. Two of the chaperones were parents in that group, so they left as well. How many individuals were left at the zoo?
<bot>: How many students went on the field trip? ** A total of 10*2=<<10*2=20>>20 students went on the field trip.
How many individuals were there? ** Some chaperones showed up, letting the group grow to 20+5=<<20+5=25>>25 individuals.
How many individuals were there? ** The teachers had to come as well, making the group as big as 25+2=<<25+2=27>>27 individuals.
How many individuals were left? ** When the school day ended, 27-10=<<27-10=17>>17 individuals were left.
How many people were left at the zoo? ** A couple of chaperones followed suit, leaving 17-2=<<17-2=15>>15 people at the zoo.
#### 15