Im pretty sure they repel from the charged protons
Explanation:
Combine like terms.
-2y + 7y = 5y
-4 - 5 = -9
So the answer would be <u>5y - 9</u>
You can classify them in what phase they are in: solid, liquid, gas
You can classify them in Sizes
You can classify them by the number of moons they have
You can classify them by distance from the sun
You can classify them all as heliocentric or orbiting/circling around the sun
You can classify them by color