Answer:
x = 25
Step-by-step explanation:
The three straight lines in the sides of the triangle means that ALL 3 SIDES ARE EQUAL.
This is an equilateral triangle. So all 3 angles are equal.
We know sum of 3 angles in a triangle is 180. Since 3 of the angles are equal, each angle is:
180/3 = 60
The top angle is given as "2x + 10", thus we can say "2x + 10" is equal to 60 degrees. Now we equate and solve for x:

The value of x is 25
The way I like to figure out problems like this is to write it out like,
1/10 = x/6000
(One over ten equals x over 6000)
Then you find out how much you multiplied 10 by to get 6000. To do this you can divide 6000 by 10 getting 600. The rule "what you do to the bottom you have to do to top" in this equation. So since you multiplied the bottom by 600 you have to multiply the top by 600 as well. 600 times 1 is just 600.
So your answer is, 600 is 1/10 of 6000.
Hope this helps and isn't too confusing.
Add all sides together to find the length of each side
40 ÷ 2.40= 16.66
the teacher can buy 16 cookies