SOLUTION: the sum of ages of dina and cora is 30. three yers ago cora was three times as old as dina. What are their present age?

Question 501422: the sum of ages of dina and cora is 30. three yers ago cora was three times as old as dina. What are their present age?
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
d = Dina's age
c = Cora's age
.
d+c = 30
so
d = 30-c
c = 30-d
.
Three years ago:
d-3 = Dina's age then
c-3 = Cora's age then
.
Cora was 3 times as old as Dina.
.
c-3 = 3*(d-3)
.
Substitute
.
(30-d) -3 = 3(d-3)
30 -d -3 = 3d -9
27 -d = 3d -9
36 = 4d
d = 9
.
c = 30-9
c = 21
.
Check your work?
3 years ago, was Cora 3 times Dina's age?
.
21-3 = 18
9-3 = 6
Yes. 3*6 = 18.
.
Answer: Currently, Cora is 21 and Dina is 9.
.
Done.
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