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
Check:
19*13 - 16*13 - 13 - 13 - 1 = 12
247 - 208 - 26 - 1 = 12
39 - 27 = 12
