Answer:
x = 13
Step-by-step explanation:
First start with the blank equation

Plug in the legs and hypotenuse. Remember c squared is always the hypotenuse.

Then solve
25 + 144 = 
169 =

c = 13
Check the picture below.
now, since we know what "f" is, let us use the CNT triangle with the small COR one.

2/3(6c+4)-(8c-5)
1) Get rid of the negative signs
New equation (the ones in bold are the changes): 2/3(6c+4)+(-8c)+(5)
2) Use distributive property for the first part by multiplying 2/3*6c= 4c and 2/3*4= 2 2/3
New equation: 4c+2 2/3+ (-8c) + 5
3) Combine like terms: 4c+(-8c)= -4c and 2 2/3+5= 7 2/3
New and simplified equation: -4c+ 7 2/3
subtract 6 from the 21x+6. Then divide by 21. The answer is going to be -6/21