How do you express $15.6$ as a mixed number?

Hint: Convert the decimal into fractional form first and you will get an improper fraction, then convert the improper fraction into mixed number.
An improper fraction can be converted into a mixed number as follows
1. Divide numerator by denominator.
2. Write quotients as a whole number.
3. And write remainder as the numerator part and divisor as the denominator part.

Complete answer:
 Here we have given a decimal number so at first we have to change this decimal form into fractional form.
To convert $15.6$ into fractional form we have to multiple its numerator and denominator by 10.
$
   = \dfrac{{15.6}}{1} \times \dfrac{{10}}{{10}} \\
   = \dfrac{{156}}{{10}} \\
 $
So we have got our required fractional form of $15.6$, that is $ = \dfrac{{156}}{{10}}$ an improper fraction.
Do you know, what is the difference between proper and improper fraction?
A proper function has its numerator value less than its denominator, whereas an improper has just the opposite property, that is, it has a numerator value greater than the denominator.
In order to convert improper fraction into mixed numbers, we have to perform a simple division of its numerator with the denominator.
$ \Rightarrow 156 \div 10 = 15$ with a remainder of 6
So here the whole number we got for the mixed number is the quotient which is $ = 15$
The numerator part $ = 6$ and the denominator part is the divisor which is $ = 10$
So we can write the required solution as $15\dfrac{6}{{10}}$
i.e. $15.6 = 15\dfrac{6}{{10}}$ which is the required mixed number.

Note: In order to convert a mixed number $\left( {a\dfrac{b}{c}} \right)$ into fractional form $\left( {\dfrac{{a \times c + b}}{c}} \right)$ or better say improper fraction, students normally gets confused and apply the wrong formula which is $\left( {\dfrac{{a \times b + c}}{b}} \right)$ instead of $\left( {\dfrac{{a \times c + b}}{c}} \right)$ which is the correct one.