Question

(a) If the total cost of a pen and a book is Rs 1200 then, write the equation representing the cost of the pen and the book. If the cost of a book is Rs. 800, what is the cost of pen? ​

Answer 1

Use substitution for this problem,

Let cost of book be X and cost of pen be Y
So, the equation is X + Y = 1200
If cost of a book is 800
Then
cost of pen = 1200 - 800 = 400