Let x and y be the number of packs with 100 and 250 paper clips, respectively. The system of linear equations that would best represent the given is
x + y = 84
100x + 250y = 12,300
The values of x and y from the equations are 58 and 26, respectively. If a person buys half of the packs of 250 paper clips,
n = (0.5)(250)(26) = 3250
Thus, a person bought 3250 paper clips.