Let us assume that , the cost of table be Rs.x and chair is Rs.y.
Case 1) :- Table at 13% gain and chair at 6% gain .
So,
→ Total gain = gain in table + gain in chair,
→ 357 = (13/100) of x + (6/100) of y
→ 357 = (13x/100) + (6y/100)
→ 357*100 = 13x + 6y
→ 13x + 6y = 35700 ------------- Eqn.(1)
Case 2) :- Table at 15% gain and chair at 8% loss.
So,
→ Total gain = gain in table - loss in chair,
→ 203 = (15/100) of x - (8/100) of y
→ 203 = (15x/100) - (8y/100)
→ 203*100 = 15x - 8y
→ 15x - 8y = 20300 ------------- Eqn.(2)
Multiply Eqn.(1) by 4 and Eqn.(2) by 3 and adding them,
→ 4(13x + 6y) + 3(15x - 8y) = 4*35700 + 3*20300
→ 52x + 24y + 45x - 24y = 142800 + 60900
→ 97x = 203700
dividing both sides by 97,
→ x = Rs.2100 .
Putting value of x in Eqn.(2) now,
→ 15*2100 - 8y = 20300
→ 8y = 31500 - 20300
→ 8y = 11200
dividing both sides by 8,
→ y = Rs.1400 (Ans.)