Your First question says what happens when you have a positive value minus a negative value.
Let the positive value be a and the negative value be - b
a - (- b) = a + b
Note
[tex]-\text{ }\times\text{ - = +}[/tex]The second question says what happens when we have a negative value minus a negative value.
-a - (-b) = -a + b
Note
[tex]\begin{gathered} -\text{ }\times\text{ + = - } \\ +\text{ }\times\text{ + = +} \\ -\text{ }\times\text{ - = +} \end{gathered}[/tex]
