The amount of fabric needed for Jimmy's costume is not stated, we can only determine the amount needed for Rob's costume, which makes it impossible to compare the amounts needed for both of their costumes. If this omission was an error, then you can find the difference between these amounts if the amount needed for Jimmy's costume is stated explicitly.
Step-by-step explanation:
The number of yards of fabric needed for Robs costume is (7/8+1/2+1 3/4)÷2
Assuming 1 3/4 is a mixed fraction.
= (7/8 + 1/2 + 7/4) ÷ 2
= (7 + 4 + 2) ÷ (8 × 2)
= 13/16 yards
Suppose 2 yards of fabric is needed for Jimmy's costume, then comparing with Rob's yards, we see that Jimmy's costume requires (2 - 13/16 = 19/16) more yards than Rob's costume.
Answer: 
Step-by-step explanation:
By definition, an Isosceles triangle has two equal sides and its opposite angles are congruent.
Observe the figure attached, where the isosceles triangle is divided into two equal right triangles.
So, in this case you need to use the following Trigonometric Identity:

In this case, you can identify that:

Substituting values, and solving for "x", you get:

Therefore, the length of BC rounded to nearest tenth, is:

I can’t do math right now but plug it into a graphing calculator (after pressing the “Y=“ button) and then press graph and you should be good