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September 25, 2016
Posted by **Lilian** on Monday, March 2, 2009 at 8:51pm.

3x = 4y

x + y = 21

Help please.

- 8th Grade Algebra -
**drwls**, Monday, March 2, 2009 at 11:28pmSubstitute 21 -x for y in the first equation.

3x = 4(21-x)

7x = 84

x = 12

y = 21-x = 9