Idon’t understand all correct answers

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

Players on the school soccer team are selling candles to raise money for an upcoming trip. each player has 24 candles to sell. if a player sells 4 candles a profit of$30 is made. if he sells 12 candles a profit of $70 is made

Which of the following circles have their centers in the third quadrant? check all that apply.