Problem 5. Nikola bought 4 different pencils. All pencils, except the first one, together cost 42 denars, all pencils, except the second one, together cost 40 denars, all pencils, except the third one, together cost 38 denars, and all pencils, except the fourth one, together cost 36 denars. How much does each pencil cost individually?
Solution. Let's denote the prices of the first, second, third, and fourth pencils with $a, b, c, d$ respectively. If we sum up all the prices, from the condition of the problem, we will find that Nikola would pay 156 denars if he wanted to buy three of each pencil. This means that Nikola actually paid a total of 52 denars for the pencils. From this, it is clear that $a=10$ denars, $b=12$ denars, $c=14$ denars, and $d=16$ denars.

## VII section - primary school
