I'll use b as the example. line JK is 33 units. it tells you how many units they are by the lines, it goes up by 6 with this one. you go up to unit30 and count the lines till k, 3 more. for line JK, ignore the negative signs and look at the units as positive numbers. from j to n there are 16 units. 30+16=JK+JN
