Assume the cost price of the article = Rs CP
Marked price =(1+0.35) CP = 1.35 CP
15 percent discount => Selling price = 1.35 CP(1-0.15)
= 1.1475 CP
Gain = Rs 88.50 => Selling price - Cost price = 88.5
1.1475 CP - CP = 88.5
CP = 88.5/0.1475
= Rs 600
Hence the cost price of the article is Rs 600.