I= prt is an example of a. a variable b. an expression c. a constant d. a formula exsplain and ill give brainliest

The answer would be 'D'. An expression does NOT have an equal sign while a formula does. A variable is some letter symbol that you are solving for, but a constant would be a number such as 2 or 4 that could be added, multiplied, subtracted, or divided in an equation. 
I hope this helps!

B. An Expression Because it not a formula i pretty sure but anyways it's an expression.

For a 0.25 pfor b o.3pp (0.25+0.3)=0.28