Вам нужно разбить то, что вы хотите, на аккуратные строки и столбцы.Затем создайте Рамку для каждой субъединицы и соедините их так, как вам нужно.
import tkinter as tk
root = tk.Tk()
leftside = tk.Frame(root)
lbl = tk.Label(leftside, text= "P(H|E)=")
lbl.pack(anchor='c')
leftside.pack(side=tk.LEFT)
rightside = tk.Frame(root)
numerator = tk.Frame(rightside)
entry1 = tk.Entry(numerator, width=5)
entry1.pack(side=tk.LEFT)
lbl = tk.Label(numerator, text='+')
lbl.pack(side=tk.LEFT)
entry2 = tk.Entry(numerator, width=5)
entry2.pack(side=tk.LEFT)
numerator.pack()
division_bar = tk.Frame(rightside, bg='black', height=4)
division_bar.pack(fill=tk.X, expand=True)
denominator = tk.Frame(rightside)
text2 = tk.Label(denominator, text= "SAA + (")
text2.pack(side=tk.LEFT)
entry3 = tk.Entry(denominator, width=5)
entry3.pack(side=tk.LEFT)
text3 = tk.Label(denominator, text= "+ [0.34])")
text3.pack(side=tk.LEFT)
denominator.pack()
rightside.pack(side=tk.LEFT)
root.mainloop()