The mass of an electron is approximately 9.109x10^-28 find the mass of 257,000,000 electrons

The base of a triangle exceeds the height by 9 inches. if the area is 180 square inches, find the length of the base and the height of the triangle.

Which statement explains how you could use coordinate geometry to prove the opposite sides of a quadrilateral are congruent? a. use the slope formula to prove the slopes of the opposite sides are the same. b. use the slope formula to prove the slopes of the opposite sides are opposite reciprocals. c. use the distance formula to prove the lengths of the opposite sides are the same. d. use the distance formula to prove the midpoints of the opposite sides are the same.

During the election for class president, 40% of the students voted for kellen, and 60% of the students voted for robbie. 500 students voted in total. how many more students voted for robbie than for kellen? answer with work : )