Let the cost of 1 bag be ‘a’ and 1 pen be ‘b’.
Given,
3 bags and 4 pens together cost Rs 257 whereas 4 bags and 3 pens together cost Rs 324.
⇒ 3a + 4b = 257 ----------- (1)
and 4a + 3b = 324 ---------- (2)
Multiplying eq1 by 4 and eq2 by 3 and subtracting eq2 from eq1.
⇒ 12a + 16b – 12a – 9b = 1028 – 972
⇒ 7b = 56
⇒ b = Rs. 8
Substituting in eq1
⇒ 3a + 32 = 257
⇒ a = Rs. 75
Cost of 1 bag and 10 pens = 75 + 10 × 8 = Rs. 155
