I think that you forgot to post a piece of your problem, so I'll assume that they are looking for the amount of miles driven that day.
The charge is $28 (which is a flat rate, meaning you will pay 28 no matter how many miles you drive) plus (+) $0.40 per mile.
Let's use the variable m for miles.
What the problem is saying is that for each m(miles) you drive you will pay $0.40. So if you drive 1 mile that will be
$0.40, and if you drive 2 miles that will be $0.80, and so on. Writing that statement mathematically will give you:
0.40m
So now we have
28 + 0.40m
The problem states that this rate plan will equal 220 for that day. (The taxes don't matter- only looking for basic bill- which is why it says before taxes.)
So now we have
28 + 0.40m = 220
So let's solve for the miles(m). Solving for something simply means you want it on 1 side of the equal sign by itself, and everything else on the other side.
So to get m by itself lets first subtract 28 from both sides.
0.40m = 192
Then we want to divide both sides by 0.40.
m=480
So the total miles driven is 480.
