The starting equation is
100=S+D+K
S is for Sarah, D is for Dave, and K is for Kate
This is what we know:
S=15+D
and
K=D-5
Now that we know how to find the values of everything, we must plug it in.
100=(15+D)+D+(D-5)
Combine like terms.
100=10+3D
Subtract 10 to isolate variable.
90=3D
Divide by 3 to isolate variable.
30=D
Plug in number to find the answers.
Answer:
Sarah worked for 45 hours
Dave worked for 30 hours
Kate worked for 25 hours
