Hint: Imagine Fred started with a large sum of money.
Imagine Fred started with £20,000, after buying the car he would have had £16,000. He then sold it to Alice, which left him with £21,000 and then bought it again leaving him £15,000. Fred finally sold it again leaving him with £22,000. So Fred's profit was £2,000.
Alternatively, you can see that Fred spent a total of £4,000 + £6,000 = £10,000 and received a total of £5,000 + £7,000 = £12,000. A difference of £2,000.
Below are five proverbs, however, each letter has been replaced by its position in the alphabet, but the spaces between the resulting numbers have been removed.
From the first statement (we take one off as Daniel is a boy):
B - 1 = G
2 * (G - 1) = B
Substitute G from the first equation into the second equation to give:
2 x ((B - 1) - 1) = B
2 x (B - 1) - 2 = B
2 x B - 2 - 2 = B
2 x B - 4 = B
B = 4
which means that B = 4 and hence G = 3.