The given expression is:
![0.3(-42)](https://img.qammunity.org/2023/formulas/mathematics/high-school/ku7n8vrv02xxs4dzjeizmz3yltjkn3ppde.png)
Rewrite the decimal outside the parentheses as a fraction:
![0.3(-42)=(3)/(10)(-42)=(3)/(10)*-42](https://img.qammunity.org/2023/formulas/mathematics/high-school/gcymca6fm4wdlcn5xn9dy6vexwh89o6vmc.png)
Multiply the numbers in the numerator and simplify:
![(3*-42)/(10)=(-126)/(10)](https://img.qammunity.org/2023/formulas/mathematics/high-school/5p8galoj7ly6qick9us3mtvwf4ocb8hind.png)
Since a division by 10 moves the decimal point to the right, it follows that:
![-(126)/(10)=-12.6](https://img.qammunity.org/2023/formulas/mathematics/high-school/81jlwedfdxv7hd7xci8rv6obi3ac0p6ukc.png)
Hence, the required answer is -12.6.