The mode is the number that shows up the most
103, 77, 90, 102, 103, 81, 78, 84, 84, 87, 99, 103, 118
reorder the numbers
77, 78, 81, 84, 84, 87, 90, 99, 102, 103, 103, 103, 118
103 shows up 3 times, one more than the next group (84)
103 is your answer
hope this helps