Question

if it costs 15.50 to make 3 widgets, 23.50 for 7, and 56.00 for 12, what does it cost to make 5?

Answer 1

This is not a linear relationship, and 3 points is not really enough to find a relationship.

The best approximation you could make is to draw the points accurately, fit a good curve to them and read the value for 5 widgets