If you have something like....
2 = 2.
You are free to add the same number to both sides.. like this:
2+1 = 2+1 => 3 = 3... still true!
You are free to subract the same number to both sides...
2-1 = 2-1 ... still true!
And so on with multiplication and division...
So if you have something like...
ab = c
And you are asked to solve for "a", you have to get all the other terms to the second member.
So what do you do is to divide by "b" to get rid of that b over there.. so you get..
a = c/b
Hope you now can do your exercise! :)