One of the most important rhythms in Blues is the triplet. A triplet is a group of three notes spaced evenly across a beat. A good way to count triplets is to count the number for each beat and then break up the word triplet for the remaining two parts of the beat. A bar of 4/4 time would be counted... One trip-let, Two trip-let, Three trip-let, Four trip-let. There are several ways of strumming triplets, but for now it is best to use all downstrokes.
Notice how each of the triplets has the number 3 in the middle.
This next one contains a new chord ... B7. Play this one very slowly at first and by sure to tap your foot and count.