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Solving Systems by Substitution Help!?

I do not understand how to do this...if you could please just write the answer and how you got it..it would help alot!! Thx

1. 4x+3y=13 and x+y=4

2. 4x-y=15 and -2x+3y=12

3. 4y-x=4 and y+x=6

4. 2x+3y=21 and -3x-6y=-24

5. 3x+y=21 and 10x+5y=65

Please no "do it yourself" or something like that..i really don't understand this...it would help alot Thx!:D

1 Answer

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  • 1 decade ago
    Favorite Answer

    1. Solve one of the equations for one of the variables. It doesn't necessarily matter which. Sometimes one is easier than the other.

    The second equation becomes x=4-y

    Plug this value into the other equation.

    4(4-y)+3y=13 and solve

    16-4y+3y=13

    3=y

    plug this into x+y=4 and solve for x

    3=x=4,x=1

    Repeat for the rest of the problems.

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