i) The LCM for 9 and 6 is 18.

\(\frac{(8\times2)}{(9\times2)}+\frac{(-11\times3)}{(6\times3)}\\\frac{16}{18}+\frac{-33}{18}\)

Since the denominators are same we can add them directly.We get

\(\frac{(16-33)}{18}=\frac{-17}{18 }\)

ii)  Firstly convert the denominator to positive number.

\(\frac{5}{-7}=\frac{(5\times-1)}{(-7\times-1)}\\\frac{-5}{7}\\=\frac{3}{1}+\frac{-5}{7}\)

The LCM for 1 and 7 which is 7

\(\frac{(3\times7)}{(1\times7)} +\frac{(-5\times1)}{(7\times1)}\\=\frac{21}{7}+\frac{-5}{7}\)

Since the denominators are same we can add them directly. We get

\(\frac{(21-5)}{7}=\frac{16}{7}\)

iii) Firstly convert the denominator to positive number then,

\(\frac{1}{-12}=\frac{(1\times-1)}{(-12\times-1)}\\=\frac{-1}{12}\)

Now,

\(\frac{2}{-15}=\frac{(2\times-1)}{(15\times-1)}\\=\frac{-2}{15}\)

So, \(\frac{-1}{12}+\frac{-2}{15}\)

The LCM for 12 and 15 which is 60.Now

\(\frac{(-1\times5)}{(12\times5)}+\frac{(-2\times4)}{(15\times4)}\\=\frac{-5}{60}+\frac{-8}{60}\)

Since the denominators are same we can add them.

\(\frac{(-5-8)}{60}=\frac{-13}{60}\)

iv) As we know that anything is added to 0 results is the same.

\(0+\frac{-3}{5}\\=\frac{-3}{5}\)

v) The LCM for 1 and 5  is 5

\(\frac{(1\times5)}{(1\times5)}+\frac{(-4\times1)}{(5\times1)}\\=\frac{5}{5}+\frac{-4}{5}\)

Since the denominators are same we can add them directly.We get

\(\frac{(5-4)}{5}=\frac{1}{5}\)