Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

Can you fill the blank with the correct number?

6 30 870 756030 _____

For an extra income, John decided to work at a Hotel for one hour daily. The manager offers him that they will pay him $11 after every 11 days.
However, John offered a different proposition to the manager. The offers stand as:
He will be paid just a penny on his first day.
Two pence will be paid on the second day,
Four pence will be paid on the third day.
And so on till the 11th day.

Should the Hotel manager accept his offer?

Can you replace the question mark with the correct number in the below table sequence?

While handling a project, the landscaper is asked by the owner of the mansion that he wants four trees in front of his mansion that are exactly equidistant from each other.

How will he do it?

Prove that the below maths equation is true.

8 + 8 = 91

Different lights make me strange by changing me into different sizes. What am I?

A Man gave one of his sons 10 cents and another son was given 15 cents. What time is it?
Hint: Figure out the relation between time and number, is not so easy..:)

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?