If the value depreciates by 20% each year it means that each year the value = 80% ( or 0.8) of the value the previous year
Lets suppose the mower cost $200 then after 5 years value would be 200 * (0.8)^5 = $6.5.54 so its not worthless
b) aFTER 2 YEARS THE FACTOR WOULD BE (0.8)^2 = 0.64
He multiplies by 0.64 Aswer