Step-by-step explanation
Let the number of hours Joe worked at the first job be x while the number of hours he worked at the second job be y.
Therefore, since he works 20 hours per week, we can say that
![x+y=20----(1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/xdqg1030inznjowix2hnz0eplxew0uk90w.png)
Also, since he made $127 in a week;
![6x+6.70y=127----(2)](https://img.qammunity.org/2023/formulas/mathematics/high-school/8gphei8ibusg6uu1pkg0e1d0c7euta4mqw.png)
Isolate for x in equation one.
![x=20-y](https://img.qammunity.org/2023/formulas/mathematics/college/wquf1c9aahuyla6axwyj8x4wiu201q220d.png)
Substitute the above in equation 2.
![\begin{gathered} 6(20-y)+6.70y=127 \\ 120-6y+6.7y=127 \\ 0.7y=127-120 \\ 0.7y=7 \\ y=(7)/(0.7) \\ y=10 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/aes0ok3q16lumq9uxt6ezbuun3377y81hz.png)
Also,
![x=20-y\Rightarrow x=20-10=10](https://img.qammunity.org/2023/formulas/mathematics/high-school/3uwsat2zj1ohsievqwx806hr1u2ztelit8.png)
Answer: Job A= 10 hours
Job B= 10 hours