Which of the following types of models is usually in the form of a drawing, graph, or equation?
a.
idea model
b.
physical model
c.
computer model
d.
none of the above

The type of model that is usually in the form of a drawing, graph, or equation would be an idea model. 

computer models are usually collections of code, physical models are usually actual physically created models that have their own characteristics. An idea model, on the other hand, is a type of model that can be explained either through a drawing, a graph, or an equation. 

I completely believe it would be an idea model. :)