A rational number is in standard or simplest or lowest form when- 

1. Numerator and denominator have only 1 as its highest common factor.

 2. Denominator is a positive integer.

 (i) The HCF of 12 and 30 is 6 

Therefore,

\(\frac{-12}{30}=\frac{-12\div6}{30\div6}\)

\(\Rightarrow\)\(\frac{-12}{30}=\frac{-2}{5}\)

(ii) The HCF of 49 and 14 is 7

 Therefore,

\(\frac{-14}{49}=\frac{-14\div7}{49\div7}\)

\(\Rightarrow\)\(\frac{-14}{49}=\frac{-2}{7}\)

(iii) The HCF of 24 and 64 is 8 

Therefore,

\(\frac{24}{-64}=\frac{24\div8}{-64\div8}\)

\(\Rightarrow\)\(\frac{24}{-64}=\frac{3}{-8}\)

In order, to make the denominator positive, multiply both numerator and denominator by -1

\(\Rightarrow\)\(\frac{24}{-64}=\frac{3}{-8}=\frac{3\times-1}{-8\times-1}\)

\(\Rightarrow\)\(\frac{24}{-64}=\frac{-3}{8}\)

(iv) The HCF of 36 and 63 is 9 

Therefore,

\(\frac{-36}{-63}=\frac{-36\div9}{-63\div9}\)

\(\Rightarrow\)\(\frac{-36}{-63}=\frac{-4}{-7}\)

In order, to make the denominator positive, multiply both numerator and denominator by -1

 \(\Rightarrow\)\(\frac{-36}{-63}=\frac{-4}{-7}=\frac{-4\times-1}{-7\times-1}\)

\(\Rightarrow\)\(\frac{-36}{-63}=\frac{4}{7}\)