Hello!
You can only add variables with the same base and exponent
8u^3 + 4u^3 = 12u^3
8u^2 + 0 = 8u^2
0 + -6u = -6u
6 + 3 = 9
Put the sums together
12u^3 + 8u^2 - 6u + 9
The answer is

Hope this helps!
To prove a similarity of a triangle, we use angles or sides.
In this case we use angles to prove
∠ACB = ∠AED (Corresponding ∠s)
∠AED = ∠FDE (Alternate ∠s)
∠ABC = ∠ADE (Corresponding ∠s)
∠ADE = ∠FED (Alternate ∠s)
∠BAC = ∠EFD (sum of ∠s in a triangle)
Now we know the similarity in the triangles.
But it is necessary to write the similar triangle according to how the question ask.
The question asks " ∆ABC is similar to ∆____. " So we find ∠ABC in the prove.
∠ABC corressponds to ∠FED as stated above.
∴ ∆ABC is similar to ∆FED
Similarly, if the question asks " ∆ACB is similar to ∆____. "
We answer as ∆ACB is similar to ∆FDE.
Answer is ∆ABC is similar to ∆FED.
We have to give counter example for the given statement:
"The difference between two integers is always positive"
This statement is not true. As integers is the set of numbers which includes positive and as well as negative numbers including zero.
Consider any two integers say '2' and '-8'. Now, let us consider the difference between these two integers.
So, 2 - 8
= -6 which is not positive.
Therefore, it is not necessary that the difference of two integers is only positive. The difference of two integers can be positive, negative or zero.
I think it might be D. I'm just giving an educated guess.