Find the value: $42.3 - 10.2$

Hint: First of all, we need to know about the operations which are used in the given problem, In general, the addition is the sum of two or more than two numbers, or values, or variables and in addition, if we sum the two or more numbers a new frame of the number will be found, similarly for subtraction which is the minus of two or more than two numbers or values but here comes with the condition that in subtraction the greater number sign will stay constant example $2 - 3 = - 1$ clearly three has the greater sign with negative thus the resultant answer is negative if suppose three is positive and two is negative then the resultant answer will be positive.

Complete step-by-step solution:
Let $42.3$ is the term of the decimal that is a fraction where the denominator is at the power of $10,100,...$ like this term $42.3$ is at the power of ten because we can rewrite this number as $\dfrac{{423}}{{10}} = 42.3$ and similarly, we can able to rewrite another term as $10.2 = \dfrac{{102}}{{10}}$ (bottom is ten)
Hence now we are going to solve this problem by converting the decimal values into rational number and then acting the subtraction operation; thus, we have :
$42.3 - 10.2 \Rightarrow \dfrac{{423}}{{10}} - \dfrac{{102}}{{10}}$
since the denominator is the same now, we combine both values as
$ \Rightarrow \dfrac{{423}}{{10}} - \dfrac{{102}}{{10}} = \dfrac{{423 - 102}}{{10}}$(now we are going to use the subtraction operator)
Hence we get,
$ \Rightarrow \dfrac{{423 - 102}}{{10}} = \dfrac{{321}}{{10}}$
Finally dividing the values, we obtain
$ \Rightarrow \dfrac{{321}}{{10}} = 32.1$
Hence for the value, $42.3 - 10.2$ we get $32.1$ as an answer

Note: We can also able solve simply by using subtraction operation; which is $42.3 - 10.2$ will get the answer as $32.1$, both methods are easy but in method one we need subtraction and division; for method two we only need subtraction.