1. A+S=180
2. A+C=90
and S=30+4C
Substituting into eq 1
A+(30+4C)=180
3. A+4C=150
Subtract eq 2 from eq 3
A+ 4C-A-C = 150 - 90
3C=60
C=20
So then
A+20=90
A = 70
70+S=180
S=110
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