SOLUTION: Match x=7y+11 3x+20y=99 12x-7y=11 3x+20y=99 which is substitution and addition method? How did you conclude your answer

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Question 179434: Match
x=7y+11
3x+20y=99
12x-7y=11
3x+20y=99
which is substitution and addition method?
How did you conclude your answer
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
We can solve the first system by substitution. We could use elimination/addition, but substitution is much easier. Why? Notice how "x" is already isolated. So we can simply plug in x=7y%2B11 in the second equation and solve for "y"


The second system can be solved much easier via elimination/addition. If we multiply the second equation by -4, we get -12x-80y=-396. If we add this new equation to equation 1, the "x" terms will cancel out which will let us solve for y.