17) slope and y-intercept

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (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.

Aclothing store has the sign shown in the shop window. pani sees the sign and wants to buy 3 shirts and 2 pairs of jeans. the cost of each shirt before the discount is $12, and the cost of each pair of jeans is $19 before the discount. write and simplify an expression to find the amount pani pays if a $3 discount is applied to her total