There are 120 liters (L) of water in the water tank. When you open the faucet in this water tank, 4 liters (L) of water flow out per minute. A few minutes after opening the faucet, 20 liters (L) of water remained in the water tank. Find how many minutes the faucet was left open.
120 20 [OP_SUB] 4 [OP_DIV]
var_a = 120
var_b = 20
var_c = var_a - var_b
var_d = 4
var_e = var_c / var_d
print(int(var_e))