9 5/6 - 2 1/3 is 7 1/2.
You could get this answer by finding the same denominator of the fractions. The LCM of both is 6. Multiply the 1 of the second fraction 2 times because you had to multiply the denominator 2 times to get to 6.
You should have 2 2/6.
Now get 9 5/6 - 2 2/6.
The answer is 7 3/6, simplifies into 7 1/2.
9 5/6 - 2 1/3 is 7 1/2.
For

, we have

and so

which is, again, only valid for

.
5 -3 * 5 5 simplified = 160!!!
7n = p+5m+3
n = (p+5m+3)/7