An atom of a certain element has 21 protons, 21 electrons, and a mass number of 45. How many
neutrons are in this atom?

Maria walks a round trip of 0.75 mile to school every day.how many miles will she walk in 4.5 days

(mc 02.03) what set of reflections and rotations would carry rectangle abcd onto itself? reflect over the y-axis, reflect over the x-axis, rotate 180° rotate 180°, reflect over the x-axis, reflect over the line y=x reflect over the x-axis, rotate 180°, reflect over the x-axis rotate 180, reflect over the y-axis, reflect over the line y=x

Abcd is a square. what is the measure of angle bac