Respuesta :

answer the answer is 7.

hhhhhhhhhhh

Answer:

width=7 cm

Step-by-step explanation:

perimeter=2(lengths+width)

        56   =2(21+x)

         56  =42+2x

   56-42  =2x

        2x    = 14

            x   =7    

therefore the width=7 cm