Which of the following demonstrates how the first 21 (on the left side of the triangle) is calculated using the combination pattern?

The correct option is A.

Step-by-step explanation:

Combination formula for selecting r items from n items is

Using the formula we get

Therefore option A is correct.

Therefore option B is incorrect.

Therefore option C is incorrect.

Therefore option D is incorrect.

b: |12 – x| ≤ 0.25

step-by-step explanation:      

let x be the possible lengths in inches, of the ribbons jaime cut.

we have been given that jaime is cutting strips of ribbon for a project. he tries to cut each piece to be 12 inches long, but sometimes he cuts it too long or too short by as much as 0.25 inch.  

we can represent this information in an inequality as:

by the definition of absolute value function we will get,

upon combining our inequalities we will get,

therefore, the inequality   describes all the possible lengths (x), in inches, of the ribbons jaime cut.

step-by-step explanation:

3

step-by-step explanation:

divide 13.5 by 9 to get the scale factor. it equals 1.5

2 * 1.5 = 3