There are 15 chickens - 3 are hens and the rest are roosters. Chicks are 4 fewer than roosters. How many chicks do you have?
15 3 [OP_SUB] 4 [OP_SUB]
var_a = 15
var_b = 3
var_c = var_a - var_b
var_d = 4
var_e = var_c - var_d
print(int(var_e))