Theory:

We can perform subtraction of rational numbers like the addition. All we have to keep in mind is the sign conversion.
Example:
Subtract 23 and 32 
As the denominator is not the same, we have to take LCM.
Here LCM is \(6\)
  
 2332=(2×2)(3×3)6=4+96=136
Let us recollect subtraction rules
We can add a negative number like
 
\(- 2 + (- 6) = - 8 \)
\( \) 
\(10 + (- 6) = 4\)
  
But how to subtract a negative number? What is \(2 - (- 6\))?
 
Let's explore what a deprivation action means.
Subtracting the second number(\(b\)) from the first number (\(a\)) means finding the difference (\(a\) number \(x\)).
\(a - b = x\)
 
The result obtained can always be verified by addition: \(x + b = a\)
\( \)
Let's follow an example \(6 - ( -4) = x\) (Let's deal with \(x\) because we don't know how to subtract yet).
 
Write the test expression \(x + (-4) = 6\)
\( \) 
Let's find the value of \(x\). How much \((- 4)\) should be added to get a positive \(6\)?

We can guess that \(x = 10\) because \(10 + (- 4) = 6.\)
\( \) 
So the unknown \(x\) is \(10.\)
\(6 - (- 4) = 10.\)
It turns out that   \((\)\() = +\)
Since we know that \(6 + 4 = 10\), we can conclude that subtract \(6\) from \((- 4)\) means add \(6\) to \(4\).
Subtracting \(b\) from the number \(a\) means adding the opposite number of \(b\) to \(a\).
Remember, \(-4\) is the opposite of \(4\).
 
There is no need to use \(x\) or any other sophisticated modifications to solve the examples, remember that \((\)\() = +\)
Example:
\(3 - (- 10) = 3 + 10 = 13\)
\( \) 
\( - 12 - ( - 3) = - 12 + 3 = - 9 \)
\( \) 
\(0.4 - ( - 0.6) = 0.4 + 0.6 = 1\)