Question 255671
Work process of Substitution 
x=4y+11
4y-5x=9 
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substitute for "x" and solve for "y":
4y - 5(4y+11) = 9
5y - 20y - 55 = 9
-15y = 64
y = -64/15
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Substitute into x = 4y+11 to solve for "x":
x = 4(-64/15)+11 = -256/15 + 165/15 = -99/15 = -33/5
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x+y=3 
x= 6-4y
Substitute for "x" and solve for "y":
6-4y + y = 3
-3y = -3
y = 1
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Substitute into x = 6-4y to solve for "x":
x = 6-4*1 = 2
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Cheers,
Stan H.