Answer:
Step-by-step explanation:
For this exercise it is important to remember the multiplication of signs:

In this case, given the following expression:

You can idenfity that both factors are negative. Then, the product (The result of the multiplication) will be positive.
Then, in order to get the product, you need to multiply the numerator of the fraction by -8. So, you get:

You can notice that the numerator and the denominator of the fraction obtained cannot be divided by the same number; therefore, the fraction cannot be simplified.
The answer would be 64 inches or 5 feet 4 inches.
3 yards is equal to 108 inches and 1 foot is equal to 12 inches which equals 120 inches
120-56=64
a)
has CDF


where the last equality follows from independence of
. In terms of the distribution and density functions of
, this is

Then the density is obtained by differentiating with respect to
,

b)
can be computed in the same way; it has CDF


Differentiating gives the associated PDF,

Assuming
and
, we have


and


I wouldn't worry about evaluating this integral any further unless you know about the Bessel functions.