So you know that a pound of rice crackers cost $42.88. You also know that Jacob bought 1/4 or 25% or 0.25 of a pound. This means that by multiplying 0.25 by $42.88, you can determine the cost.
0.25 x 42.88 = 10.72
Therefore, Jacob paid 10.72 cents or $10.72 for 1/4 pound of rice crackers