Bob can make 7 leashes in 2 hours, which means he can make 7/2 leashes in 1 hour. Nina can make 4 leashes in 1 hour.
It means that together, they can make 7/2 + 4 leashes in 1 hour. Use this information to write the equation required to find how many hours would it take for them to make 60 leashes.
Solve the sum in the parentheses to find the required equation in the simplest form:
That is the equation that can be used to find the number of hours it takes for them to make 60 leashes.
Now, solve the equation for t to find the number of hours it takes for them to make the 60 leashes.
It takes 8 hours for them to make 60 leashes.