7,200 ÷ y = 90 equals
y = 80.
First, multiply both sides by y. / Your problem should look like: 7200 = 90y.
Second, divide both sides by 90. / Your problem should look like:

= y.
Third, simplify

to 80. / Your problem should look like: 80 = y.
Fourth, switch sides. / Your problem should look like: y = 80, which is the answer.