The cost of having photos taken includes a sitting fee and $12 for each portrait.the cost of 3, 6, and 9 photos respectively is $51, $87, and $123. What is the sitting fee?
+2592 3*12=36
That is the cost of the portraits in the first exampls
51-36=15
15 is the sitting fee
6*12=72
Cost of second example
87-72=15
9*12=108
third example
123-108=15
So for all three examples, the sitting cost is $15
