The milk that Suyeong's family drank today is 0.4 of the total amount. If the remaining milk is 0.69 liters (L), how many liters (L) of milk were there at the beginning?
0.69 1 0.4 [OP_SUB] [OP_DIV]
var_a = 0.69
var_b = 1
var_c = 0.4
var_d = var_b - var_c
var_e = var_a / var_d
print('{:.2f}'.format(round(var_e+1e-10,2)))