Answer:
27 years old
Step-by-step explanation:
What I know
Let D = Dave, S = Sabrina, etc. Then:
(1) [tex]D=0.15S[/tex]
(2) [tex]L=0.75S[/tex]
(3) [tex]R=3.00D[/tex]
(4) [tex]D+S+L+R=141[/tex]
Want to find R. Taking equation 3 and rewriting equation 4, we get
[tex]R=3.00D[/tex]
[tex]R=141-D-S-L[/tex]
So if [tex]R=R[/tex], then
[tex]3D=141-D-S-L-R[/tex]
[tex]4D=141-S-L[/tex] by adding [tex]D[/tex] to both sides.
Using equation 1 and equation 2, I can rewrite everything in terms of [tex]S[/tex] and get:
[tex]4(0.15S)=141-S-0.75S[/tex]
[tex]0.6S=141-1.75S[/tex]
[tex]2.35S=141[/tex] by adding [tex]1.75S[/tex] to both sides.
[tex]S=60[/tex] by dividing 2.35 both sides.
Now that I know Sabrina's age, I'll work towards getting Rhianna's using equation 1 and equation 3:
[tex]D=0.15(60)=9[/tex]
[tex]R=3.00(9)=27[/tex]
Checking my work:
Dave: 9
Sabrina: 60
Luca: 45 (since 9+60+45+27=141)
Rhianna: 27
9 is 15% of 60
45 is 75% of 60
27 is 300% of 9
