Expression: $-12-\left( -8 \right)+\left( -3 \right)$
When there is a $-$ in front of an expression in parentheses, change the sign of each term of the expression and remove the parentheses $-12+8+\left( -3 \right)$
When there is a $+$ in front of an expression in parentheses, the expression remains the same $-12+8-3$
Calculate the sum or difference $-7$