Please consider the complete question.
Michelle bought the same fabric on 3 different occasions and recorded the data below.
Yards of Fabric Total Cost
2.2 $2.53
3.6 $4.14
4.2 $4.83
What was the price per yard of fabric?
To find the cost per yard of fabric, we will divide cost of yards by number of yards.
Let us find cost per yard using 2nd set of data.
Similarly we will find cost per yard for 3rd set of data.
Therefore, the cost per yard of fabric is $1.15.
The sum of the inner angles of any triangle is always 180°, i.e. you have
In the particular case of an equilater triangle, all three angles are the same, so
and the expression becomes
which implies
So, if you rotate the triangle with respect to its center by 60 degrees, the triangle will map into itself. In particular, if you want point A to be mapped into point B, you have to perform a counter clockwise rotation of 60 degrees with respect to the center of the triangle.
Of course, this is equivalent to a clockwise rotation of 120 degrees.
Finally, both solutions admit periodicity: a rotation of 60+k360 degrees has the same effect of a rotation of 60 degrees, and the same goes for the 120 one (actually, this is obvisly true for any rotation!)