Saif,
I'll show you how to solve this problem by solving a similar problem:
Saif buys 2.5 kg of carrots and 5 kg of potatoes. He pays a total of £8.55. The price of the potatoes is £0.90 per kg. What is the price per kg of the carrots?
a) The cost of the potatoes is the amount of potatoes (5 kg) times the price per kg of potatoes (£0.90 per kg).
b) The cost of the carrots is the amount of carrots (2.5 kg) times the price per kg of carrots, which we don't yet know. Let's call the price of the carrots C.
c) The cost of the potatoes plus the cost of the carrots is the total bill, which is £8.55.
As a mathematical equation, this means:
5(0.90) + 2.5(C) = 8.55
and we can simplify this:
4.50 + 2.5C = 8.55
and then solve for C:
4.50 + 2.5C  4.50 = 8.55  4.50
2.5C = 4.05
2.5C / 2.5 = 4.05 / 2.5
C = 1.62
So the price per kg of the carrots is £1.62. Now you try it with your question.
Stephen La Rocque.
