FX Equation includes a calculator that you can use to simplify the entry of solutions.
Video - The FX Equation Calculator
To use the calculator, select a part of your entered equation and then push the Calculator Button
FX Equation will evaluate the selection you have made and placed the value onto the clipboard. You can paste it in on the next line.
The calculator allows you to create solutions to questions without reaching for your trusty scientific calculator.
Often a better approach is to use the "Inline" calculator, particularly if you are using Parameters.