Answer:
The value of y is 3 cm.
Step-by-step explanation:
Given,
Perimeter of triangle = 
Solution,
Lets redraw the triangle with nomenclature ABC, given in the attachment.
∴P(ΔABC) = 29 cm (P stands for perimeter)
Length of AB = 
Length of BC = 
Length of CA = 
Now, we all know that the perimeter of a triangle is sum of all the three sides of triangle.
P(ΔABC) = Length of AB+Length of BC+Length of CA
On substituting the values, we get;

Length of AB =
Length of BC =
Length of CA =
Hence the value of y is 3 cm.