Fisile decomposition from one field resulting from the withdrawal to another Tkinter

[gionna]

Help me get this straight. As a Tkinter programme, remove a window where a call for a number will be made and the number will be added to the previously introduced number after a call to add up. The volume in one field needs to be inserted by number (infinite number of times) and in another the amount will be removed. I don't know how to get the money out.

from tkinter import *
from tkinter import messagebox
import math
def calculation():

num = int(a.get())

num2 = int(b.get())

num2 = num2 + num
root = Tk()

root.title("Додавання чисел")

root.geometry("400x150")
a = StringVar()

b = StringVar()

Label(root, text="Введіть число").place(x=20, y=20)

Entry(root, textvariable=a).place(x=115, y=10)

Label(root, text="Отримуємо").place(x=20, y=55)

Entry(root, textvariable=b).place(x=115, y=55)
but = Button(text="Додати", command=calculation).place(x=200, y=100)
root.mainloop()

[carriann]

Call. b.set(...) in the right places.

from tkinter import *
from tkinter import messagebox
import math
def calculation():

num = int(a.get())

num2 = int(b.get())

num2 = num2 + num

b.set(str(num2))
root = Tk()

root.title("Додавання чисел")

root.geometry("400x150")
a = StringVar()

b = StringVar()

b.set("0")

Label(root, text="Введіть число").place(x=20, y=20)

Entry(root, textvariable=a).place(x=115, y=10)

Label(root, text="Отримуємо").place(x=20, y=55)

Entry(root, textvariable=b).place(x=115, y=55)
but = Button(text="Додати", command=calculation).place(x=200, y=100)
root.mainloop()