Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

No matter how little or how much you use me, you change me every month. What am I?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

what one word does the below rebus identifies?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

John was a very careless driver, so his owner Jacob gave him an offer that he will get an incentive of Rs.30 for every bottle box he delivered without breaking it and he will be charged Rs.90 for every bottle box he broke. Jacob gave John 100 bottles-box to deliver. After delivery, Jacob paid John Rs.2400. How many bottles-box did John break?

Can you write down eight eights so that they add up to one thousand?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?