Few questions explain too, very confused

1. twice the difference between a number and ten
2. if 5 is subtracted from twice a number the result is 11
3. if 5 is added to the quotient of a number and 4 , the result is 10
4. associative property use: 4x5n

1).
Call the number 'N'.
The difference between the number and ten is  (N-10).
Twice the difference between the number and ten is  2(N-10).
That's all the question asks for.  There's no way to find what number 'N' is.

2).
Call the mystery number 'Q'.
Twice the number is  2Q.
If  5  is subtracted from twice the number, you have  (2Q - 5).
But it tells us that the result would be  11 .
So write  (2Q - 5) = 7    and solve that simple equation to find what 'Q' is. 

3).
Call the mystery number 'Z'.
The quotient of the number and 4 is  Z/4.
If you add 5 to the quotient of the number and 4, you have  (Z/4 + 5).
It tells us that the result would be  10.
So write  (Z/4 + 5) = 10 and solve that simple equation to find what 'Z' is.

4).
I'm sorry.  I don't know what this question is asking for.

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)