Let the price be x. The chain the gives:

(1st) 1x-0.2x=0.8x

(2nd) (1-0.15)(1x-0.2x)=0.68x

(3rd) (1-0.1)(0.68x)=0.612x

The net price equivalent rate is 0.612=61.2% of the original price.

(1st) 1x-0.2x=0.8x

(2nd) (1-0.15)(1x-0.2x)=0.68x

(3rd) (1-0.1)(0.68x)=0.612x

The net price equivalent rate is 0.612=61.2% of the original price.