Ok, adding into the explanation what the heck this kind of a table is. The "stem" column is the tens place of each of the children's weights. The "leaf" is the ones digit of each of the children's weights. So in the row where the stem is 2, there were 2 kids weighing 23 and 25 pounds.
For your question, we have to add up how many students have a weight with a "stem" less than 5, because that's where 50 pounds starts.
8 + 2 + 5 + 3 = 18 children weighed less than 50 pounds.
