Meritnation experts Why we multiply Both numerator and denominattor by 100i did not understand at all????? In this case????

This was actual Q21 plz check one of Meritnation experts Multiplied by 100 on both sides why i did not understand????

Because i want to remove Both decimal point and write in Whole number

Meritnation experts in Q21 can you remove Decimla point and write in Whole number so it will be easy to divide in whole number but i do not know so teach me how to do That

This is question i need to remove Decimal i need full explanation how to Remove point and write in Whole number and then divide it will be easy so asking????