Can you find out the missing number in the grid?

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

Which country gets ill every time?

What is the word or phrase?

I am white when I am dirty, and black when I am clean. What am I?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

On my way to St. Ives I saw a man with 7 wives. Each wife had 7 sacks. Each sack had 7 cats. Each cat had 7 kittens. Kittens, cats, sacks, wives. How many were going to St. Ives?

Can you decipher the following common phrase?

T M C
A U O
H S M
W T E