How much does one pencil cost?

In a stationery store, pencils have one price and pens have another price. Two pencils and three pens cost 78¢. But three pencils and two pens cost 72¢. How much does one pencil cost?

Let cost of one pencil = P
and cost of one pen = N

Two pencils and three pens cost 78¢
i.e; 2P+3N=78¢ .........(1)
Three pencils and two pens cost 72¢
i.e; 3P+2N=72¢ .........(2)

Solving equations (1) and (2)
(1) × 2 is
4P+6N=156 ......(3)
(2) × 3 is
9P+6N=216 ......(4)

(4) - (3) 
5P=60
=> P=12

Cost of one pencil is 12¢.