I need this please determinant topic

Ineed with angles and the measure of them i have abc a is 65 and b is (3x-10) and c is (2x) find the value of x

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.

Campus rentals rents 2 and 3 bedrooms apartments for $700 ans $900 a month respectively. last month they had six vacant apartments and reported $4600 in lost rent. how many of each type of apartment were vacant?