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,

(ii) The HCF of 49 and 14 is 7

Therefore,

(iii) The HCF of 24 and 64 is 8

Therefore,

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

(iv) The HCF of 36 and 63 is 9

Therefore,

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