“Using an overhead projector back at the Interior Ministry, Mr. Wuoma attempts to explain the math. He takes out a piece of paper covered with long equations, which seem more appropriate for a college class in nuclear physics.
The equations start with a motorist’s net monthly income. The figure comes into play whenever a driver is caught going at least 12 miles an hour over the posted limit (below that, the fine is a fixed amount, ranging from $63 to $110). To begin, the driver’s monthly net income is reduced by 255 Euros ($235) and that total is divided by 60. This figure is supposed to represent a person’s daily disposable income.
[That] figure, called a day fine, is then multiplied by a number ranging between one and 120, representing the severity of the violation as determined by the traffic officer. For example, a person driving 20 miles an hour over the limit on a highway in good weather might be assessed 12 day fines.”
Using this information, you can get the rough formula of:
Money owed = Daily disposable income * severity of violation
Breaking it down further you get:
Money owed = ((Motorist’s net monthly income – 255) / 60) * severity of violation
If we assume that we are dealing with “Speeding 25 km/h, speed limit over 60 km/h” as described in the story (12 day fines) we get:
Money owed = ((Motorist’s net monthly income – 255) / 60) * 12
y = 12((x – 255)/60)
where y represents the money owed and x represents the motorist’s net monthly income.