Find the factors of:

$18$

Find the factors of:

$25$

Find the factors of:

$36$

Find the factors of :

$42$

Find the HCF using common factors:

$\mathrm{12,16}$

Find the HCF using common factors:

$15,35$

Find the HCF using common factors:

$27,54$

Find the HCF using common factors:

$31,37$

Find the LCM of :

$7,9$