#1 Nope. 5/6 + 2/3 = 5/6 + 4/6 = 9/6
#2 ok
#3 Nope. 9 is a perfect square.
#4 Nope. Suppose x = 1/6. You have 1x/2x
#5 ok
#6 ok
#7 ok
#8 Nope. A has too many -7's
#9 What's the difficulty? Just use the values given:
2s³-4r² if r=1 and s=5
2*5³-4*1²
2*125-4*1
250-4
246