Can someone help me out my grads are bad

The measure of one angle of an octagon is two times smaller that of the other seven angles. what is the measure of each angle?

Which questions would most a reader identify the author's purpose for writing? check all that apply. what type of text is this? what type of reviews did the book receive? how many copies of the book have been sold? what is the central idea? how does this text make one feel?

3x + 4y = 5 x- 3y = -7 solve by substitution