Solving Systems by Substitution Help!?

Question

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

snapdragon · Accepted 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.

Solving Systems by Substitution Help!?

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