I don't see any exercise, but the equation that you typed looks like the formula for the circumference of a circle, in terms of the radius.
C = 2 * Pi * r
The symbols C represents the circumference, and the symbol r represents the radius.
3.14 is a decimal approximation (rounded to two decimal places) for the famous constant Pi.
When you typed ";r" at the end of the equation, is that supposed to mean that you've been asked to solve the equation for r ?
If so, then "solve for r" means to get the symbol r all by itself, on one side of the equals sign.
You can do this by dividing both sides of the equation by (2 * Pi).
Otherwise, I don't know what you're trying to ask.