Posted by **Nadia** on Tuesday, November 24, 2009 at 1:24pm.

please solve by method of substitution

0.3x-0.4y-0.33=0

0.1x + 0.2y -.21=0

please give all steps to solve.I think I understand the basic concept but this is little more complicated for me. Thanks in advance

- college algebra -
**MathMate**, Tuesday, November 24, 2009 at 3:40pm
Things look a lot easier if you multiply each equation by 100 and simplify, and transpose the constants to the right hand side.

30x - 40y = 33 .....(1)

10x + 20y = 21 .....(2)

From equation (2), transpose 20y to the right and divide equation by 10 to get

10x = 21 - 20y

x = 2.1 -2y .... (3)

Substitute x into equation (1) to get

30(2.1-2y) - 40y = 33

63 - 60y -40y = 33

-100y = 33-63

-100y = -30

y=(-30)/(-100)

=0.3

Substitute y=0.3 into (3) to get

x=2.1-2(0.3)

=1.5

Now, substitute these values of x=1.5 and y=0.3 into the original equations to make sure the solution is correct.

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