SOLUTION: how do you solve by substitution: 0.1x + 0.9y = -4.3 0.5x - 0.4y = 3

Algebra ->  Expressions-with-variables -> SOLUTION: how do you solve by substitution: 0.1x + 0.9y = -4.3 0.5x - 0.4y = 3      Log On


   

Question 772234: how do you solve by substitution:
0.1x + 0.9y = -4.3
0.5x - 0.4y = 3
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
.1x+%2B+.9y+=+-4.3+
+.5x+-+.4y+=+3+
I would multiply both sides of both
equations by +10+
(1) +x+%2B+9y+=+-43+
(2) +5x+-+4y+=+30+
------------------
Solve (1) for x
(1) +x+=+-9y+-+43+
Substitute this result into (2)
(2) +5%2A%28+-9y+-43+%29+-+4y+=+30+
(2) +-45y+-+215+-+4y+=+30+
(2) +-49y+=+245+
(2) +y+=+-245%2F49+
(2) +y+=+-5+
and
(1) +x+=+-9%2A%28+-5+%29+-+43+
(1) +x+=+45+-+43
(1) +x+=+2+
------------------
check:
+.5x+-+.4y+=+3+
+.5%2A2+-+.4%2A%28-5%29+=+3+
+1+%2B+2+=+3+
+3+=+3+
OK