\(-\left(-630\right)+915+\left(-630\right)+\left(-615\right)\)
\(=630+915-630-615\)
\(=915-615\)
\(=300\)
-(-630)+915+(-630)+(-615)
= 630 + 915 - 630 - 615
= (630 - 630) + (915 - 615)
= 0 + 300
= 300
\(-\left(-630\right)+915+\left(-630\right)+\left(-615\right)\)
\(=630+915-630-615\)
\(=\left(630-630\right)+\left(915-615\right)\)
\(=0+300\)
\(=300\)