Respuesta :

Answer:

d = 13

Step-by-step explanation:

19d - 16d - d - d - 1 = 12

19d + (-16 - 1d - 1d) - 1 = 12

19d + (--18d) - 1 = 12

19d - 18d - 1 = 12

1d = 12 + 1

d = 13

Check:

19*13 - 16*13 - 13 - 13 - 1 = 12

247 - 208 - 26 - 1 = 12

39 - 27 = 12