Answer:
Base Fee = $7
Extra charges = $7
Explanation:
Represent the base charge with x and the additiional charges with y.
For the 5 hours job, we have:
![42 = x + 5y](https://img.qammunity.org/2021/formulas/mathematics/high-school/dv359jdp5ohxu2eur5njmrxdlcdjwfxbie.png)
For the 3 hour job
![28 = x + 3y](https://img.qammunity.org/2021/formulas/mathematics/high-school/1s7wezt891otg4wi4xyi7x705mnc3x30h8.png)
Solving for x and y;
![42 = x + 5y](https://img.qammunity.org/2021/formulas/mathematics/high-school/dv359jdp5ohxu2eur5njmrxdlcdjwfxbie.png)
![28 = x + 3y](https://img.qammunity.org/2021/formulas/mathematics/high-school/1s7wezt891otg4wi4xyi7x705mnc3x30h8.png)
Subtract the second equation from the first
![42 - 28 = x - x + 5y - 3y](https://img.qammunity.org/2021/formulas/mathematics/high-school/a4d6u4ahmibwamadr6lkgaoce25urfo42c.png)
![14 = 2y](https://img.qammunity.org/2021/formulas/mathematics/high-school/spayzzsdqygddva247n30ymgjnuriaax2a.png)
Solve for y
![y = 14/2](https://img.qammunity.org/2021/formulas/mathematics/high-school/klyb8ci3n8d32mvezb866vmfsinkzf5yee.png)
![y = 7](https://img.qammunity.org/2021/formulas/mathematics/high-school/zme1i4bq6ucitsu280yhg5iimattvy4g9m.png)
Substitute 7 for y n the first equation
![42 = x + 5y](https://img.qammunity.org/2021/formulas/mathematics/high-school/dv359jdp5ohxu2eur5njmrxdlcdjwfxbie.png)
![42 = x + 5 * 7](https://img.qammunity.org/2021/formulas/mathematics/high-school/5k2pwxvtx8rxrero7ow7xx2jh59q2dsp7c.png)
![42 = x + 35](https://img.qammunity.org/2021/formulas/mathematics/high-school/pb3a8289jgpuooxxygrs6i7ugim3ek6gr6.png)
![x = 42 - 35](https://img.qammunity.org/2021/formulas/mathematics/high-school/ubfyn2y2s4u31ysz44cyi1ygqxe0ghc7hy.png)
![x = 7](https://img.qammunity.org/2021/formulas/mathematics/middle-school/haui06dyzu06cccqprdnwfvnybjm6zc7di.png)