Building and solving a system of equations, we find that:
a) The system is:


b) The solution is:

c) Replacing into the equations, we get:


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As stated in the problem:
- b is the number of hours babysitting.
- w is the number of hours walking dogs.
Item a:
Total of 75 hours, thus, the first equation of the system is:

$15 for each hour babysitting, $20 for each hour walking the dog, and a total of $1350, thus:

Then, the system of equations is:


Item b:
From the first equation, we write w as function of b, to find b in the second: 
Replacing in the second:







Then, for w:

The solution is:
.
Item c:
To verify, we just replace the solutions into the two equations:


A similar problem is given at brainly.com/question/24823220