Use Your Knowledge of English: 

1. Analyze the Units of the Answer. How many dimensions?

Insurance statistics state that a person loses 8 minutes of average life for each cigarette smoked. If there are 20 cigarettes in a pack and the average cost of cigarette is $5.00 per pack over the next 25 years, how many years of average life would a person lose for smoking 1.5 packs a day for 25 years?

Years Average Life are Time units: a single (simple) dimension with a label Average Life!

2. Is there a single dimension 'number and unit' not connected to a Unit Factor in the problem?

"25 years of smoking" is also a single dimension of Time with a smoking label which can be connected to the Single Dimension Time Unit of the Answer with life lost label!

3. Equate the given to the unit asked for in the answer.

_???__years avglife = 25 yearssmoking