Solution:

See the figure for the answer. Wasn't it a bit tricky?

Solution:

I am on cloud 9.

Solution:

David to play second

Explanation:
Let's suppose that David plays first and he picks 9. Then Albert will definitely pick 8. Now, David will have to pick 7 or Albert will pick 7 in his turn. But if David picks up 7, then he will score 16 that is beyond 15 and will lose. So one thing is for sure, no one will be willing to start with the highest digits.

Suppose David plays first and picks up 1, Albert will pick 2. Then David will pick 3 and Albert will pick 4. Now David will be forced to pick 9. The score is 6 to 13 and thus David will have no chance of winning.

If David Picks 9 after Albert has picked up 2, then Albert will pick 8 and the score will become 10 to 10. Thus David will pick 3 as picking 7 will send him past 15. Now Albert will pick 4 and David has nothing to pick for winning. Thus Albert wins.

Therefore, you should suggest David to play second.

Solution:

O=2, N=3, E=5, T=6, H=9, R=7, L=0, V=1, W=4, Y=8

Thus,
235 + 235 + 235 + 69755 + 69755 + 505153 = 645368

Solution:

The words are:

1. LIMP
2. IDEA
3. MEAT
4. PATE

Solution:

17

Explanation:
Let us say that the smallest of the square is of 1 unit side.
We have 6 such squares. Now moving up, if we see the squares with side 2 units, we have 8 of them. Similarly we have 2 squares with side 3 units and 1 square with side 4 units.

6 + 8 + 2 + 1 = 17 squares.

Solution:

It is one of the classic riddles. Just be careful how you are adding and you will find out.

Your mother gave you Dollar 300 and you gave her back Dollar 3. So in original, she spent just Dollar 297 on the goods. Out of those Dollar 297, Dollar 295 are with the shopkeeper and Dollar 2 were spent by you on candies.

Solution:

split personality

Solution:

Two people.

The question mentions that a couple went to see a wildlife sanctuary. There is no mention that the rest of the people went along.

Solution:

Let us solve this problem with the help of diagonals. We know, that the sides of square are parallel. Therefore, the diagonals should also be parallel. See the picture, the yellow diagonals are drawn for referencing.

See the image, you can easily spot the four triangles highlighted with red color.

Now, in this picture, you can spot 3 blue, 3 green and 2 red squares. You can find four more rectangles but they can't be square as their diagonals are not parallel with our yellow referenced diagonals.

Therefore, total number of squares = 4 + 8 = 12.