from tkinter import *

root = Tk()
root.title('Listbox - Tabuada')
root.geometry('400x400')
root.config(bg='#03f8fc')
def showSelected():
    a = lb.get(ANCHOR)
    show["text"] = '\n'.join([
        "{x} * {y} = {result}".format(x=int(a),
                                      y=n,
                                      result=int(a) * n)
        for n in range(1, 11)])
   # show.config(text=lb.get(ANCHOR))
lb = Listbox(root,justify='center')
lb.pack()
lb.insert(0, 1)
lb.insert(1, 2)
lb.insert(2, 3)
lb.insert(3, 4)
lb.insert(4, 5)
lb.insert(5, 6)
lb.insert(6, 7)
lb.insert(7, 8)
lb.insert(8, 9)
lb.insert(9, 10)
lb.select_set(2)
Button(root, text='Mostrar Resultado', command=showSelected, font=("Arial","12")).pack(pady=20)
show = Label(root, font=("Arial","9","bold"),fg="#bf9000",bg="#03f8fc")
show.pack()
root.mainloop()