5% of 8.72. 0.0436 0.436 4.36

You can set up an inequality with each of these. is/of = %/100

In this case you'd be solving for each of the "is".

(1) X/8.72=5/100

100X = 43.6

X =.436

(2) X/0.0436=5/100

100X=0.218

X = 0.00218

(3) X/0.436=5/100

100X=2.18

X=0.0218

(4) X/4.36=5/100

100X=21.8

X=0.218

I've heard of the method referred to as the Heart Method. Try looking up YouTube videos on how to solve these types of problems.