Oftentimes it’s easier to divide a number by powers of 10 (like 10, 100, 1000 etc.) because all you need to do is move the invisible decimal place left by how many zeros you have in the power of 10. The problem is that the denominator sometimes isn’t a power of 10 – like this in problem, 10 is not a power of 10.

So, what do we do? We can convert this fraction into a power of 10! If the denominator is a factor of a power of 10, like 2, 4, 5, 8, 10, 16, 20, 25, 40, 50 and so on, then we can convert them into a power of 10.

How? Multiply by the numerator (top) and denominator (bottom) by the same amount that makes the denominator to a power of 10. To make 10 a power of 10, we need to multiply by 1 (10 * 1 = 10). Now if we multiply the denominator by 1, we also need to multiply the numerator by 1 too:

$\frac{79 * 1}{10 * 1} = \frac{79}{10} = 7.9$

And finally, you get 7.9 as your answer when you convert 79/10 to a decimal.