Riddle #20 Answer
the number "7" on the phone keypad

Riddle #19 Answer
Answer:
There are three possible solutions for this 51 and 15. 42 and 24. 60 and 06.

Riddle #18 Answer
Answer
1. mustards + (RATS - mu_STAR_ds)
2. frosting + (NITS - fro_STIN_g)
3. consumes + (EMUS - con_SUME_s)
4. tastable + (BATS - ta_STAB_le)

Riddle #17 Answer
11=6
12=6
The number of letters in the words: eleven, twelve

Riddle #16 Answer
Answer: 11  letters in the  phrase "The Alphabet"

Riddle #15 Answer
Answer: dozens

Riddle #14 Answer
Answer
Giant to Big to Bit to Bite to Chew to Hew to Chop.

Riddle #13 Answer
Answer: His horse is named Friday!

Riddle #12 Answer
Answer: When you add two hours to eleven o'clock, you get one o'clock.

Riddle #11 Answer
In 2148 contact was made with Zeta in the Albati system with a population of 10 million.
In 2161 contact was made with Mu in the Polaris system with a population of 8.5 million.
In 2202 contact was made with Pi in the Electra system with a population of 15 million.
In 2217 contact was made with Rho in the Betelgeuse system with a population of 12 million.
In 2238 contact was made with Kappa in the Wezen system with a population of 9.5 million.

Riddle #10 Answer
Answer: "therein": the,there, he, in, rein, her, here, ere, therein, herein.

Riddle #9 Answer
The men who went hunting were: A grandfather, his son & his grandson

Riddle #8 Answer
The letter "n"

Riddle #7 Answer
Footsteps

Riddle #6 Answer
The letter "M"

Riddle # 5 Answer
The letter e. End, timE, spacE, Every placE