Add and subtract the values. Express your answer in scientific notation. (6.15x 10^8)-(2.5x 10^7)+(3.4 x 10^9)
6.24 x 10^8
7.05x 10^8
3.99 x 10^9
4.04 x 10^9

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?

When the ball has traveled a distance of

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.