To find the molarity (M) of a solution, you can use the formula:
\[ M = \frac{\text{moles of solute}}{\text{liters of solution}} \]
In this case, you have 3.0 moles of KBr and a solution volume of 850.0 mL. First, you need to convert the volume from milliliters to liters.
\[ 850.0 \text{ mL} = 0.8500 \text{ L} \]
Now you can plug the values into the formula:
\[ M = \frac{3.0 \text{ moles}}{0.8500 \text{ L}} \approx 3.5294 \text{ M} \]
Thus, the molarity of the solution is approximately 3.5294 M.