18 is the result of multiplying a number by 2. What do you get when you subtract 4 from this number?
18 2 [OP_DIV] 4 [OP_SUB]
var_a = 18
var_b = 2
var_c = var_a / var_b
var_d = 4
var_e = var_c - var_d
print(int(var_e))