Your problem shows a pair of equivalent ratios.
To determine the value of n, you need to figure out the relationship between the denominators 1/2 and 1. Because you can multiply 1/2 by 2 to get 1 , you need to determine what number, n, times 2 is equal to 6. That number (or n) would be 3.
So 3 :1/2 = 6/1