Answer:
The answer is option D: 42.
Step-by-step explanation:
First we have to understand that for every 20 students there is one teacher we can find this form the ratio 20:1. Then we are given that there are 840 students. That means for every 20 students in the 840 there is one student. And, 840 divided by 20 equals 42. (please give brainliest)
