Triangles have 3 vertices. The total is 21 vertices. 21 / 3 = 7. He drew 7 triangles.
2 solutions, the root to the equation is the same as the root to the solution also known as “double roots”
He spends $8.24 all together
Either or can be used with any triangle...I personally find the law of sines is often more compact as in this case we can just say;
(sin115)/18=(sin40)/c (with no need for b or B as would be needed with the law of cosines...)
c=18(sin40)/(sin115)
c≈12.77
$52.95 - $2.50 = $50.45
$50.45 divided by 5 (number of people) = $10.09 per person