What must be subtracted from -3 to get -9?

Hint: For solving this question we will use the general mathematical calculation. As we know that if we add any negative value in negative value then it will be reduced and if we add any positive value in the negative value that it will be less negative value. And if we subtract the negative value from the negative value then it will be increased and it will be less negative and if we subtract a positive value from a negative value then it will be reduced or it will become more negative.

Complete step by step solution:
According to our question we have to ask to find a number which will be subtracted from -3 to get -9.
As we know that if we add any positive value in any positive value then our resultant number is increased and if we add any negative value in the positive value then the resultant value will be reduced than the original positive value. And if we subtract to the positive number from a positive number then too the resultant will be reduced and if we subtract any negative value from any positive value then it will be increased from the original positive main value.
And if we see this for negative values then if we add.
So, if we see the given numbers -3 and -9.
As we can see here that -3 is greater than -9. And this -9 will be resultant with -3 if we subtract any positive value from that so if we see the difference of both then it is 6.
So, if we subtract 6 from -3 then:
\[\begin{align}
  & =-3-\left( 6 \right) \\
 & =-3-6 \\
 & =-9 \\
\end{align}\]
So, we will subtract 6 to get -9.

Note: While solving this type of question it has to be reminded that we add to the negative and positive values with positive value and subtract them as the same then it will be resulted as a reduced and increased. And this same applied for the negative values.