Hi there! Hopefully this helps!
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Answer:
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![-30=5k+5](https://img.qammunity.org/2021/formulas/mathematics/high-school/yyappe7dy0fkecs9hiik7jk0717yslysvl.png)
Swap sides so that all variable terms are on the left hand side.
![5k+5=-30](https://img.qammunity.org/2021/formulas/mathematics/high-school/2njyr4zesxyzkfaaai070jhy32czji70iq.png)
Subtract 5 from both sides.
![5k=-30-5](https://img.qammunity.org/2021/formulas/mathematics/high-school/fonuevbfzpxxt31vj8nqd9ceu3sul61xow.png)
Subtract 5 from −30 to get −35.
![5k=-35](https://img.qammunity.org/2021/formulas/mathematics/high-school/xyf8079x8ck8l82h83h9jgef64w7jtfgz3.png)
Divide both sides by 5.
![k=(-35)/(5)](https://img.qammunity.org/2021/formulas/mathematics/high-school/r7u0r1h57ogkm0n69l5kkowd2yjjtje0xs.png)
Divide −35 by 5 to get, you guessed it, -7!
You can also do "5(-7) + 5 = ??" For proof.