70% of the kids are taking horseback riding lessons
Number of lessons: 210
The number of kids (x) multiplied by the percentage that is taking horseback riding lessons in decimal form (70/100) must be equal to the number of lessons (210)
x (70/100) = 210
Solve for x
0.7x=210
x= 210/0.7
x= 300
There are 300 kids at the camp roan altogether.