Ateacher spends hour grading of a student's essay. at
this rate, how long does it take the teacher to grade the
student's entire essay?

Step-by-step explanation:

A: x = 12-4 = 8

B: x =  12/4 = 3

No wonder you asked for help. Some of the questions don't make sense!

x+3 = 9 ⇒ x=6, which doesn't match either A or B.

3·x = 9 ⇒ x=3, which matches B

9 = 3·x is the same as the previous equation, i.e., B.

3+x = 9, doesn't match either A or B.

x = 9-3, doesn't match either A or B

x = 9÷3 ⇒ x=3, which matches B

x+x+x = 9 ⇒ x=3, which matches B

I'm guessing that there is an error in tape A, and x should be 6, not 8.