4. The answer is the number of letters in the number. Six has 3 letters, twelve has 6 letters and four has 4 letters.

It’s a palindrome (a word or phrase that’s spelled the same backwards and forwards).

Her birthday is December 31st. Today is January 1st so she was 7 two days ago, and turned 7 last year. Now she’s 8 and will turn 9 this year. And next year she’ll turn 10.

For example, if today is 01 Jan 2015:

30 Dec 2014 = age 7 (two days ago)
01 Jan 2015 = age 8 (today, she turned 8 on 31 Dec 2014, which was last year)
31 Dec 2015 = age 9 (her birthday this year)
31 Dec 2016 = age 10 (her birthday next year)

X (10), L (50), C (100), D (500), M (1000). They’re Roman numerals in order from smallest to largest.

Light the first fuse on both ends and the second fuse at only one end. When the first fuse burns out you know 30 minutes have passed. Light the other end of the second fuse and when it burns out, 45 minutes have passed.