Lisa tapes three 7inch by 9inch pieces of construction paper together to make a happy birthday sign for her mom. she uses a piece of ribbon that is 144inches long to make a border around the outside edges of the sign. how much ribbon is left over

Depends on how the papers are connected. if they are connected with the 7cm side joining each other, use solution one. if they are connected with the 9cm side joining each other, use solution two.

perimeter of edges of sign= 2 [(9x3)+7]
= 68 inches

left over= 144-68
= 76 inches

OR

perimeter of edges of sign= 2[(7x3)+9]
= 60 inches

left over= 144-60
= 84 inches

Two because two of one thing is two.