Can someone help me with these two questions and can you show your work please and thank you

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

The estimated number of people to attend the last bengals game of the season was 2000. the actual number of fans attending was 1200. by what percent did the estimate differ from the actual?

Find the area of the triangle formed by the origin and the points of intersection of parabolas y=−3x^2+20 and y=x^2−16.