import tkinter as tk
window = tk.Tk()
entry = tk.Entry()
entry.grid(row=0,column=0,columnspan=3)
l1 = tk.Label(text="10%", width=3)
l1.grid(row=1, column=0)
l2 = tk.Label(text=16500, width=7)
l2.grid(row=1, column=1)
window.mainloop()

 import tkinter as tk
window = tk.Tk()
entry_var = tk.StringVar()
entry_var.trace('w',  lambda name, index, mode :(l2.config(text=int(entry_var.get())*1.2)))
entry = tk.Entry(textvariable=entry_var)
entry.grid(row=0,column=0,columnspan=3, )
l1 = tk.Label(text="10%", width=3)
l1.grid(row=1, column=0)
l2 = tk.Label(text=16500, width=7)
l2.grid(row=1, column=1)
window.mainloop()