Here is your answer:
6.78 rounded to the nearest tenth = 7.00 because the 7 in 6.78 is greater then five.
8.21 rounded to the nearest tenth= 8.00 because the 2 in 8.21 is NOT greater than five.
81 cubic feet are in 3 cubic yards.
To answer this problem, one way is to use the calculator and add directly the two numbers and get the average between the two. The answer is 25/77. We can also get this number by getting the LCM of the denominators which is 77. 2/7 is equal to 22/77 while 4/11 is equal to 28/77. 0.5*(22 +28) is equal to 25. Hence the answer is 25/77.
I had this same question yesterday it was c 2x+3x+9x