Pls help me! (question is in the picture)

In triangle abc, the length of side ab is 12 cm, the length of side bc is 5 cm, and the length of side ca is 9 cm. find the measure of angle a using the law of cosines.

How many real and imaginary solutions does the equation x^2-3x=-2x-7 have?

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.