1. The same three letters, in the same order, can precede the two words below to make two new words.

_ _ _ IRE
_ _ _ TEEN

2. The same three letters, in the same order, can follow the two words below to make two new words:

COP _ _ _
TAX _ _ _

Answers:

1. The letters are UMP:

UMPIRE
UMPTEEN

2. The letters are IES:

COPIES
TAXIES