## Task 2 - 060612

At the beginning of the school year, Heinz bought two different types of notebooks, one costing 8 Pf, the other 15 Pf per piece. He paid 1.31 MDN for 12 notebooks in total.

How many notebooks did he buy of each type?
Let $a$ be the number of notebooks costing 8 Pf and $b$ the number of notebooks costing 15 Pf. Then we have

$$
a \cdot 8 + b \cdot 15 = 131 \quad ; \quad a + b = 12 \quad \text{or} \quad a = 12 - b
$$

Substituting the second equation into the first, we get $8 \cdot (12 - b) + 15b = 131$. From this, we find $b = 5$ and further $a = 7$.

Heinz buys 7 notebooks costing 8 Pf and 5 notebooks costing 15 Pf.