(i) Since, the denominators of given rational numbers are negative therefore, we will make them positive.

\(\frac{7}{-18} = \frac{7\times-1}{-18\times-1} = \frac{-7}{18}\)

Now, 

since, the denominators of given rational numbers are different therefore, we take their LCM.

LCM of 18 and 27 = 54

\(\frac{-7}{18} = \frac{-7\times3}{18\times3} = \frac{-21}{54}\)

And

\(\frac{8}{27} = \frac{8\times2}{27\times2} = \frac{16}{54}\)

Now,

\(\frac{-7}{18}+\frac{8}{27}\)

= \(\frac{-21}{54}+\frac{16}{54}\)

= \(\frac{-21+16}{54}\)

= \(\frac{-5}{54}\)

(ii) Since, the denominators of given rational numbers are negative therefore, we will make them positive.

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

And,

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

Now, 

since, the denominators of given rational numbers are different therefore, we take their LCM. LCM of 12 and 15 = 60

\(\frac{-1}{12} = \frac{-1\times5}{12\times5} = \frac{-5}{60}\)

And

\(\frac{-2}{15} = \frac{-2\times4}{15\times4} = \frac{-8}{60}\)

Now,

\(\frac{-5}{60}+\frac{8}{60}\)

= \(\frac{-5+(8)}{60}\)

= \(\frac{-5-8}{60}\)

= \(\frac{-13}{60}\)

(iii) We can write \(-1\) as \(\frac{-1}{1}.\)

Now,

since, the denominators of given rational numbers are different therefore, we take their LCM. 

LCM of 1 and 4 = 4

\(\frac{-1}{1} = \frac{-1\times4}{1\times4} = \frac{-4}{4}\)

And

\(\frac{3}{4} = \frac{3\times1}{4\times1} = \frac{3}{4}\)

Now,

\(-1+\frac{3}{4}\)

= \(\frac{-4+3}{4}\)

= \(\frac{-1}{4}\) 

(iv) We can write 2 as \(\frac{2}{1.}\)

Now, 

since, the denominators of given rational numbers are different therefore, we take their 

LCM. LCM of 1 and 4 = 4

\(\frac{2}{1} = \frac{2\times4}{1\times4} = \frac{8}{4}\)

And

\(\frac{-5}{4} = \frac{-5\times1}{\times1} = \frac{-5}{4}\)

Now,

\(2+\frac{-5}{4}\)

= \(\frac{8+(-5)}{4}\)

= \(\frac{8-5}{4}\)

= \(\frac{3}{4}\)

(v) \(0+\frac{-2}{5}\)

On adding, any number to 0 we get the same number. 

Therefore,

\(0+\frac{-2}{5}= \frac{-2}{5}\)