Answer:
3 years -> value decreases by 20% 3 times
20% -> value is 80% of the original price
1st year value (after 20% decrease) = S15,500×[tex]\frac{80}{100}[/tex]
                              = S12,400
2nd year value (after 20% decrease) = S12,400×[tex]\frac{80}{100}[/tex]
                               = S9,920
3rd year value (after 20% decrease) = S9,920×[tex]\frac{80}{100}[/tex]
                              = S7,936