Question 698755
Solution:
Let us assume that the cost price of the all three television set is x, 
now selling price of each television set is:
1st TV set SP = $x , 
2nd TV set SP = 20% of x + x 
= 0.2 x + x 
= 1.2x 
3rd TV set SP = 15% of x + x 
              = 0.15x + x 
              = 1.15x 

total amount he recived after selling the television set is: $670 
hence we get: 
x + 1.20x + 1.15x = 670 
3.35x = 670 
x = 670/3.35 
x = 67000 / 335 
x = $200
hence the cost price of the each television is $200.