Remember that
If two figures are similar, then the ratio of their corresponding sides is proportional
In this problem
triangle ABC is similar t triangle XYZ
that means
AB/XY=BC/YZ=AC/XZ
substitute given values
4.8/3.2=a/5.2=6/y
Part 1
Determine the length side a
so
4.8/3.2=a/5.2
a=(4.8/3.2)*5.2
a=7.8
Part 2
Find out the length of side y
4.8/3.2=6/y
y=(6/4.8)*3.2
y=4