Math quiz! Please help.

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

Find the exact value of each of the following. in each case, show your work and explain the steps you take to find the value. (a) sin 17π/6 (b) tan 13π/4 (c) sec 11π/3

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.