Mr. young has a piece of rope. he uses 1/4 of it to tie some boxes together. he then uses 5/9 of the remainder to make a jumprope for his daughter. after this, 120 centimers are left. what is the length of rope mr. young used to tie the boxes together?

We have:

 x= the amount of rope.
 x(boxes)= the amount of rope used to tie the boxes together.

 Then, we have the following equation:

 x-(1/4)x-5/9(x-(1/4)x)=120
 (x-4/x)-(5x/9)+(5x/36)=120
 (1/3)x=120
 x=120x3
 x=360 cm

 x(boxes)=(1/4)360
 x(boxes)=360/4
 x(boxes)=90 cm

 What is the length of rope Mr. Young used to tie the boxes together?
 The lenght  of rope Mr. Young used to tie the boxes together is: 90 cm.