Answer: The width of the garden/fence will be 15 m.
Step-by-step explanation: First, we have to understand that there will be two wide sides and two long sides, and in a rectangle, the long sides always equal each other and the wide sides equal each other as well. This means that one width and one length will equal 120/2=60.
In other words:
one length of the garden + one width of the garden = 60
Now that we know this, we move on to the "3 times" part of the question. For this step, it is easiest to imagine quarters of something, because 3/4 of something will always be 3 x 1/4 of something; The proportion for 3/4:1/4 will always be 3:1.
60 x 3/4 is equal to 45 and 60 x 1/4 is equal to 15.
To check our answer, L+W+L+W = 45+15+45+15 = 120.
This means each wide side is equal to 15.