<PRE><B>Question 1082568</B>
5x + 10y = 12 (15(0.8)) multiply both sides times 2
2x + 3x = 3.9 (5(0.78)) multiply both sides times -5 and add to the other equation
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10x + 20y = 24
-10x + -15y = -19.5
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0x + 5y = 4.5
5y = 4.5
y = 0.9 = 90%
plug this into one of the original equations to solve for x.
5x + 10(0.9) = 12
= 0.6 
try the other equation if you want to double-check:
2x + 3(0.9) = 3.9
= 0.6</PRE>