Final answer:
If Lucinda has $18 to spend and both kewpie dolls and beanie babies cost $6 each, she would buy 3 beanie babies and 0 kewpie dolls.
Step-by-step explanation:
Lucinda has $18 to spend and the price of both kewpie dolls and beanie babies is $6 each. In order to determine how many of each she would buy, we need to divide her total budget by the price of one doll or one beanie baby. If she spends all her money on kewpie dolls, she can buy $18 / $6 = 3 dolls. If she spends all her money on beanie babies, she can buy $18 / $6 = <<3=3>>3 beanie babies. Since the question asks for a rational decision, Lucinda would choose to buy 3 beanie babies and 0 kewpie dolls.