Can someone help me understand this and give me the answer?

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.

Factor the polynomial expression x6 – x3 – 20

Answer each of the questions for the following diagram: 1. what type of angles are these? 2. solve for x. what does x equal? 3. what is the measure of the angles?