But y dun hv to put 11?

I dun understand

132k =( 2^2 x 3 x 11) x (2^2 x 3 x 5)

= 2^4 x 3^2 x 5 x 11

= 720 x 11

There is no need to put 11 as the factors of 132 already includes 11.

The idea here is to find the smallest positive integer k such that 132k is a multiple of 720.

This is done by including prime factors into k
such that 132k has all the prime factors of 720.

So, the prime factors in 132k that 720 does not have will thus be the multiple of 720. In this case,
132 has the prime factor 11 but 720 does not.

So, 132k has all the prime factors of 720 + prime factor 11 (which 720 does not have).

So, 132k= 720 x 11 (as shown above)