Posted by **Sara** on Saturday, December 8, 2012 at 8:32am.

8s+ 12 = 16, 6s+ 9t = 12 solve by substitution

- Algebra -
**Reiny**, Saturday, December 8, 2012 at 10:37am
I think you have a typo and you should have 12t in the first equation

If so, then drwls made the following observation

http://www.jiskha.com/display.cgi?id=1282324238

- Algebra -
**khan**, Saturday, December 8, 2012 at 11:43pm
8s+12=16............. equation 1

6s+9t=12............. equation 2

Multiply equation 1 by 3 and equation 2 by 4 and subtract.

+24s+36= +48

+24s+36t=+48

- - - (sign will change when sub)

.............

36-36t=0

t=1

put t=1 in equation 2

6s+9(1)=12

s=1/2

CHECK 6(1/2)+9(1)=12

12=12

LHS=RHS so your answer is correct

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