Question 324027
Let C be Carla's age, D her daughter's.
1.{{{C=4D}}}
In 30 years, 
2.{{{(D+30)=(1/2)(C+30)}}}
Substitute eq. 1 into eq. 2,
{{{2D+60=4D+30}}}
{{{2D=30}}}
{{{highlight(D=15)}}}
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{{{highlight(C=4(15)=60)}}}
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The daughter is 15, Carla is 60 years old.