To define a variable, use the := operator.
To make a variable 'a' with a value of 5 type.
a:=5
hit ENTER
So far the variable has not been defined. It has only been prepared to become defined. To actually execute the command type.
result
hit ENTER
The stack should not have a variable called "done!". You can delete it by typing
pop
hit ENTER
Defining functions is very similar to defining variables.
To make a function f(a,b) that returns a^2+b type.
f(a,b):=a^2+b
hit ENTER
Now to execute the definition type.
result
hit ENTER
The syntax is solve(equation,variable)
Suppose the equation in question is 3x^2-2x-7=0 type
solve(3*x^2-2*x-7=0,x)
hit ENTER
result
hit ENTER
The solutions to that quadratic should be returned.
You can also ask the problem in a more english like query like...
What are the roots to 3*x^2-2*x-7 in terms of x