Question 214189
How do you solve by substitution of linear equation? 
2x+y=9 
y=x-3
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The 2nd eqn has y isolated, so sub for y into the 1st eqn.
2x+y=9
2x + (x-3) = 9
3x - 3 = 9
3x = 12
x = 4
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y = x-3 = 4-3
y = 1