Caleb practices piano 20 minutes per day, and he practices guitar 30 minutes per day. Which expression represents the number of minutes Caleb spends practicing instruments after d days? Select each correct answer.

Answer:20d + 30d = 50dStep-by-step explanation:We know the variable d represents the number of days.He practices piano 20 minutes per day; this gives us the expression 20d.He practices guitar 30 minutes per day; this gives us the expression 30d.Together, this gives us20d + 30d; combining like terms gives us50d.