6. The answer is 17. Convert the fractions 3/4 and 5/2 to decimals, which would be 0.75 and 2.5. then add all the numbers to find your answer.
7. The answer is 0.7. Convert the fraction 3 1/2 to 3.5, and then subtract 3.5 and 2.8 to find your answer.
8. The answer is 6.5. Convert 1 3/5 and 5/4 to decimals, which would be 1.6 and 1.25. Then add 1.6, 1.25, and 3.65 to find your answer.
I really hope this helps!