Posted by **harry** on Thursday, April 10, 2008 at 3:40am.

can you solve this equation by using simultaneous equations and can you write the method please?

Sarah and Louise have a combined age of 24. Six years ago Sarah was triple Louise's age. What is Sarah and Louise's ages now. Let Sarah be x and Louise be y.

thankyou

Harry

- math -
**Damon**, Thursday, April 10, 2008 at 4:55am
S + L = 24

(S-6) = 3 (L-6)

solve first for L

L = (24 - S)

Multiply second out

S - 6 - 3 L - 18

S = 3 L -12

substitute our L from the first equation in the second equation

S = 3 (24 - S) - 12

S = 72 - 3 S -12

4 S = 60

S = 15

then use the first equation to find L

L = 24 - 15

L = 9

then check

Now

15 + 9 = 24 , yes they add to 24 check

Six years ago

15-6 = 9

9 - 6 = 3

sure enough, 9 is three times 3, check

- math - Typo fix -
**Damon**, Thursday, April 10, 2008 at 4:57am
S + L = 24

(S-6) = 3 (L-6)

solve first for L

L = (24 - S)

Multiply second out

S - 6 = 3 L - 18

S = 3 L -12

substitute our L from the first equation in the second equation

S = 3 (24 - S) - 12

S = 72 - 3 S -12

4 S = 60

S = 15

then use the first equation to find L

L = 24 - 15

L = 9

then check

Now

15 + 9 = 24 , yes they add to 24 check

Six years ago

15-6 = 9

9 - 6 = 3

sure enough, 9 is three times 3, check

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