AppleScript Calculator

set r to return as text
display dialog "Choose an operation" buttons {"Add", "Subtract", "Other"} with title "Calculator"
set opr to button returned of the result
-- You pressed add
if opr is "Add" then
    display dialog "Enter your first number in the equation" default answer "" with title "First Number"
    set FirstNumber to text returned of the result
    display dialog "Your curent equation is " & FirstNumber & "+?" & r & "Enter your second number" default answer "" with title "Second Number"
    set SecondNumber to text returned of the result
    display dialog "Your equation is " & FirstNumber & "+" & SecondNumber & r & r & "Answer: " & FirstNumber + SecondNumber buttons {"OK"}
    -- you picked subtract
else if opr is "Subtract" then
    display dialog "Enter your fisrt number in the equation" default answer "" with title "First Number"
    set FirstNumber to text returned of the result
    display dialog "Your curent equiation is" & FirstNumber & "-?" & r & "Enter your second number" default answer "" with title "Second Number"
    set SecondNumber to text returned of the result
    display dialog " your equation is" & FirstNumber & "-" & SecondNumber & r & r & "Answer: " & FirstNumber - SecondNumber buttons {"OK"}
else
    display dialog "Pick your operation" buttons {"Multiply", "Divide"}
    set X to button returned of the result
    -- You picked multiply
    if X is "Multiply" then
        display dialog "Enter your first number in the equation" default answer "" with title "First Number"
        set FirstNumber to text returned of the result
        display dialog "Your curent equation is" & FirstNumber & "*?" & r & "Enter your second number" default answer "" with title "Second Number"
        set SecondNumber to text returned of the result
        display dialog "Your equation is" & FirstNumber & "*" & SecondNumber & r & r & "Answer:" & FirstNumber * SecondNumber buttons {"OK"}
    else
        display dialog "Enter your first number in the equation" default answer "" with title "First Number"
        set FirstNumber to text returned of the result
        display dialog "Your curent equation is" & FirstNumber & "/?" & r & "Enter your second number" default answer "" with title "Second Number"
        set SecondNumber to text returned of the result
        display dialog "Your equation is" & FirstNumber & "/" & SecondNumber & r & r & "Answer:" & FirstNumber / SecondNumber buttons {"OK"}
    end if
end if