teaser.py

import numpy as np

a = np.array([[6, 0, 0], [2, 2, 2], [0, 1, 3]])
b = np.array([30, 20, 13])
[shoe, boy, whistle] = np.linalg.solve(a,b)
print("\nshoe=", shoe, "\nboy=", boy, "\nwhistle=", whistle)
print("shoe + boy * whistle = ", shoe + boy * whistle)