Question

the cost of 5 books and 7 pens is Rs 79 and the cost of 7 books and 5 pens is rupees 77 find the cost of one book and two Pen

Answer 1

let cost of one book is b
and one pen is p

eq 1 is
5b+7p=79
b=(79-7p)/5


eq2 is
7b+5p=77

put value of b in eq2
7(79-7p)/5 + 5p=77
553-49p+25p=77*5
553-385=24p
p=168/24
p=7

cost