Hi Manisha,

Ok, Hindi me batata hu.

Dekho 6 - 3 = 3 hana, ab agar 3*9 kr de to 27 ho jata h.

Aise hi, 5 - 4 = 9 hana, ab agar 1*9 kr de to 9 ho jata h.

Bilkul aise hi, 6 - 4 = 2 hana, to ab isko bhi 2*9 karenge or answer hoga 18.

Simple h na.

Koi dikkat ho to comment kr dena.

Mujhe lagata h ki tumhe samjh aa gya hoga,

Good Luck!