Answer: The total number of fifth graders in the school is 155.
Step-by-step explanation: Given that at Brown Elementary School, 80% of all fifth graders ride the bus to school.
If 124 fifth graders ride the bus to school, we are to find the number of fifth graders in the the school.
Let, 'n' be the total number of fifth graders in the school.
Then, according to the given information, we have

Thus, the total number of fifth graders in the school is 155.