16y^2/72y^6

To simplify this expression, we can first simplify the numerator and denominator separately.

Numerator:
16y^2

Denominator:
72y^6

Now, we can simplify the expression by canceling out common factors between the numerator and the denominator.

16y^2 / 72y^6
= (16/72) * (y^2 / y^6)
= 2/9 * 1/y^4
= 2/9y^4

Therefore, the simplified expression is 2/9y^4.