There are 360 degrees in the rhombus which means the equilateral triangles has 180 degrees (because it is half the rhombus and also it is the angle sum of a triangle). It is equilateral meaning all sides and angles are the same so they all must be 60 (180/3)
Now this must mean that angle a is equal to the opposing angle being 60
The number of natural numbers less than n is n-1.
Natural numbers are whole and positive numbers that are not 0.
If n is 2, there is one natural number less than n... and that is 1.
If n is 5, there are four natural numbers less than n... which are 1, 2, 3, and 4.
= 318
And the calculator can help you on problems like this
Hope That Helped =D