You have to calculate a subtraction between two negative numbers:
[tex]-7-(-3)[/tex]Note that there are two minus signs after another in the expression. This situation is called a "double negative" and when it happens, the minus signs cancel each other and become positive:
[tex](-)(-)=(+)[/tex]You can write the expression as:
[tex]\begin{gathered} -7-(-3) \\ -7+3 \end{gathered}[/tex]Now you can solve the calculation
[tex]-7+3=-4[/tex]