The correct answer is 12 teeth
Step-by-step explanation:
The ratio represented by the diagram is 6:1 or 6/1, this means, for each 6 teeth in the larger gears there is only 1 in the smaller gear. Now, to find the number of teeth if the larger gear is 72 the best is to use cross multiplication. The process is shown below:
1. Write the known values, and use x to represent the value missing

2. Use cross multiplication, and then division to find x


3. Solve the operation