split RichTextbox into 3 parts

Hey gys wanna help

i have 4 textboxes = num1, num2, result and sym
and i have one richtextbox

all textboxes are empty else richtextbox

in richtextbox i type = 4 + 5

i wanna when the user click butoon
'''check the rich textbox

if (richtextbox.text.contains("+"))
{
sym.text == "+";

and here my problem wanna got the number which left in sym and right in sym ant typed in num1.text and num2.text then do collect then the result will put in result.text

sym = + its example i wanna +, - and *

plzzz :)