The manager of a store went to check what had been the selling price in 2006 of a television from the VejoTudo brand. He found a faded invoice, which read: "lot of 72 VejoTudo TVs sold for $R \$ \ldots 679 \ldots$ reais", where the digits in the units and ten-thousands place were illegible. What was the selling price in 2006 of each of these televisions?
Let $a$ be the ten-thousands digit and $b$ be the units digit. Since the number is divisible by $72=8 \times 9$, we have that $79b$ is an even number divisible by 8. Testing the values of $b=0,2,4,6$ and 8, we see that $b=2$. A number is divisible by 9 if the sum of its digits is a multiple of 9. Therefore, $a+6+7+9+2=a+24$ is a multiple of 9. Thus, $a=3$. Therefore, each TV costs: $36792 \div 72=511$ reais.