Brain Teasers and Puzzles 

Workings

Hint
One of the names is MEL.

Answer
demi----     + john  = demijohn
---ple       + sam   = sample
absor---t    + ben   = absorbent
he---che     + ada   = headache
sc----r      + anne  = scanner
----ionaire  + bill  = billionaire
break---ce   + dan   = breakdance
monog---     + amy   = monogamy
-----incense + frank = frankincense
s---ly       + mel   = smelly

Workings

Hint
There are three feet in a yard, and 1,760 yards in a mile.

Answer
Seconds in a week.

Reasoning
There are 60 x 60 x 24 x 7 = 604,800 seconds in a week.

There are 3 x 1760 x 100 = 528,000 feet in 100 miles.

Workings

Hint
The word begins with the letter S.

Answer
SWIMS.

Workings

Hint
Think of Roman numerals.

Answer
Delta.

Take the Roman numerals in sequence, and convert to the phonetic alphabet.
  1 = I = India
  5 = V = Victor
 10 = X = X-Ray
 50 = L = Lima
100 = C = Charlie
500 = D = Delta