Which figure has rotational symmetry? Question 21 options: a) butterfly b) chalkboard c) half of an apple

B) Chalkboard.

Step-by-step explanation:

Ok, so basically you need to know what rotational symmetry is. Rotational symmetry is the property a shape has that when rotated some amount of degrees less than 360, it looks the same as it was without being rotated at all.  

So, basically it means that the figure can be rotated and it will look as though it hasn't been rotated at all.

Starting off with the butterfly, it is clear that even when rotated it will never look the same as it was without being rotated (you can click on the image rotation function to see this).

Next, looking at the chalkboard, it is obvious that when rotated 180 degrees, it will look the same as it looked without being rotated (click the rotate image button twice). So, this will be our answer.

answer: b.48 for

step-by-step explanation:

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".