## Task B-1.2.

When asked how many minutes she spends on social networks daily, Iva answered: "The nonuple of that number is between 1100 and 1200, and the tridecuple is between 1500 and 1600." How many minutes does Iva spend on social networks daily?
## Solution.

Let $x$ be the desired number.

Then $9 x \in\langle 1100,1200\rangle$ and $13 x \in\langle 1500,1600\rangle$

It follows that $x \in\{123,124,125, \ldots, 133\}$ and $x \in\{116,117, \ldots, 123\}$.

The desired number is 123.