SOLUTION
From the question, we want to find the probability of selecting a slip of paper with the letter t on it, then selecting the letter r, with replacement.
This means the probability of selecting t and r.
That is

There are 12 letters (total outcomes). And there are 2r and 2t.
So probability becomes

Hence the answer is
If x is fish, y is octopi, and z is crabs, then you would have to know the numbers.
Then your answer would be c. 30x+80y-15z.
Because x=+30, y=+80, and z=-15.
I hope that helps. If you need any further help on this problem just ask.
Solution: Z= -9
Reasoning: -6 - 3 = -9
A^2+ b^2= c^2
24^2+b^2=25^2
576+b^2=625
Sub 576
b^2= 49 b=7
30^2= 30×30=900 so 30^2 is the answer