SOLUTION STEPS:
  1. Since tenths and thousandths are equal, call that digit "d". Hundredths is d-1.
  2. The sum: d + (d-1) + d = 20. So 3d - 1 = 20, 3d = 21, d = 7.
  3. Digits: tenths=7, hundredths=6, thousandths=7 -> 0.767.