CPhill

cos 72  = 15 / x       multiply both sides by x and divide both sides by cos 72.....this gives

x = 15 / cos 72  =  about 48.54

2/x + 9 = 16     subtract 9 from both sides

2/ x = 7            multiply both sides by x

2 = 7x              divide each side by 7

2 / 7 = x

Assuming a normal year of 365 days, just compute

130,490 / 365

-9 - - 4

Remember that two negatives multiplied together produce a positive.....so we have....

-9 + 4  =

-5

The sum of the first n odd numbers = n^2

And the number of odd terms is given by [1 + n] / 2

So we have

[1 + 3983] / 2 = 1992 terms

So 

1992^2 / 1992 =

1992

i believe we have

sin^(2)x + 5 sinx - 3= 0      we could make a substitution and use the quadratic formula, but I prefer a graphical approach

The price per bag =

9.00 / 20 = 

.45  =  45 cents

z^(1/2)  = 40

Square both sides

z = 1600

There are 12 times 30 degrees  = 360 degrees in a circle

So 5 people represent 1/12 of the total.

So 12 times 5 = 60 people in total

There are several ways to do this.......let's find 1/2 of a side length of the octagon

We have

(1/2)s/sin22.5 = 4.5/ sin 67.5

(1/2)s = [4.5 sin 22.5] / sin67.5 = about 1.864

So we have 8 triangles with heights of 4.5 and a side length of about 3.728

So, the area is given by

8 * (1/2) *3.728 * 4.5  = about 67.1 sq units