Answer:
Well to estimate a decimal the best option would be to round it to.
10 or 11 (For 10.9)
11 (For 11.1)
and since two of them equal 11.
The estimation would be 11.
I hoped this helped.
Answer:

Step-by-step explanation:
If a Rectangle has a perimeter of 40 units, then we can write that formula and find the a formula for the coordinates:

Therefore we can say:

Technically when
in this rectangle is a square, a degenerate square.
Answer: 
Step-by-step explanation:
For this exercise it is important to remember the multiplication of signs. Notice that:

In this case you have the following expression given in the exercise:

Then you can follow the steps shown below in order to solve it:
Step 1: You must solve the subtraction of the numbers 0,65 and 3,21. Then:

Step 2: Now you must find the product of the decimal numbers above. In order to do that you must multiply the numbers.
(As you can notice, both are negative, therefore you know that the product will be positive).
Then, you get that the result is the following:

Answer:
5
Step-by-step explanation:
? x 2 = 10
/2 /2
? =5