PLEASE HELP I AM CONFUSED.

What are “like terms”? why can we only add like terms?

Which of the following equations are equivalent to -2m - 5m - 8 = 3 + (-7) + m? -15m = -4m -7m - 8 = m - 4 -3m - 8 = 4 - m m - 4 = -7m - 8 -8 - 7m = -4 + m -8 - 3m = 4 - m

The area of a circle is equal to 1 dm². find the radius of the circle.