Question

stefan is three years younger than his sister katie. The sum of Stefans age three years ago and 2/3 of katies age at that time is 12.How old is Katie now. Show your work

Answer 1

If x is the age of S

And y is the age of K

So we have x=y+3

And the second equation is x-3 + 2/3)y = 12

We have to solve the system

x-y=3

x+2/3y=15

we find x=10.2 and y=7.2

so Katie is 7 

Answer 2

Katie's age be k, then staefan's age = k - 3
(k - 3) - 3 + 2/3(k - 3) = 12
k - 6 + 2/3k - 2 = 12
5/3k - 8 = 12
5/3k = 12 + 8 = 20
k = (20 x 3) / 5 = 60/5 = 12 years.

Therefore, katie's age is 12 years old.