To answer this question, we have to substract 1/4 (which is the part of the pizza Santa ate) from 5/12 (the part of the pizza that was left over).
[tex]\frac{5}{12}-\frac{1}{4}=\frac{20-12}{48}=\frac{8}{48}=\frac{1}{6}[/tex]1/6 of the pizza was left when Santa finished eating.
