We can add 1/6 & 1/3 together to find out the total amount of crackers that were eaten:
1/6 + 1/3 (Find the Common Denominator. In this case it is 6.) = 1/6 + 2/6 = 3/6 (Now find the Lowest Terms. Both 6 & 3 divide into 3) = 1/2 (In Lowest Terms)
This means that 1/2 of the Crackers have been eaten.
Essentially what you want to do is count how many units each dot is from the line l and then count the same amount of units to the right. For example, point b is 3 units from line l so the dot b' would be 3 units to the right of the line l.