What is B ?

Find x :

\(x\left\{{}\begin{matrix}x+x\\x-x\\x\times x\end{matrix}\right.\)

If a is the even number, the total of a + a is the even number or the odd number?

Give that the rectangle ABCD as shown. Prove that : the perinmeter of the rectangle ABCD is equal the area of the rectangle ABCD.

Give that \(A=x+2x+3x+4x+...\)

a) Shortern A ?

b) Find \(x\) for \(A=x+2x+3x+...=x\)?

Give that : \(3x+y=\overline{yx}\); calculate \(x+y\)

Inside the marble bag, there are 10 marbles. 4 of them are blue marbles. If Kate picks out 1 marble without looking, what is the probalility after he picks out the marble ? Express your answer as a common fraction.

Joe has 15 marbles. 2 of them are blue marbles, 4 of them are purple marbles. What fraction show that the number of red marble ?

Jason has $8. He going the bookstore to buy 2 books. If each book cost 1 dollar; 2 quarters; 3 dimes; 2 nickel; 4 cents, how much money he has left ?

List the middle point:

Find the area of the shaded region in the shape below:

Find the 100th number:

10, 21, 32, 43, 54, 65, 76, 87, 98, 109, ...

Linda has 12 marbles. After play with Tony, she loses 3 marbles.

a) What fraction suppose number marbles Linda has left? Express your answer as a common fraction.

b) If in the first time Tony have 8 marbles, how many marbles will Tony have now?

If box A fit inside box B, box B fit inside box C, box C fit inside box D; how many boxes fit inside the box D ?

A) 1

B) 2

C) 3

After Lina used the box, she ranks the box as shown. If each edge is 30cm long, find the area on the shadow region? Express your answer in 2 ways. 

What is the area of the shaded region in the picture below?

See that if you can determine the rules and come up with the last number.

Example:55::57::...  Answer:59.

a)68::108::...

b)200::280::...

How many diffent ways you can divide the number 308 in the group, if know that each number in the group is equal and the group has no less than 2 number?

Find x, such that: \(\left(x\times x\right)^x\times x^x=\left(x\times x\times x\right)^x\)

Give that A= 87235-80106+(987+12). Prove that A is the perfect number.