SOLUTION: I need help with substitution. x+3=y 3x+4y=7 with steps & answers please and thank you

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Question 638983: I need help with substitution.
x+3=y
3x+4y=7
with steps & answers please and thank you
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
substitution.
x + 3 = y
3x + 4y = 7
:
From the 1st equation we know that: y = (x+3)
Substitute (x+3) for y in the 2nd equation
3x + 4(x+3) = 7
:
multiply what's inside the brackets
3x + 4x + 12 = 7
:
Add the x's, subtract 12 from both sides
7x = 7 - 12
7x = -5
x = -5%2F7
:
Find y
y = x + 3
substitute -5%2F7 for x
y = -5%2F7 + 3
Change 3 to 7ths
y = -5%2F7 + 21%2F7
y = 16%2F7
:
Solution: x = -5%2F7; y = 16%2F7
:
:
Check solution in the 2nd equation
3x + 4y = 7
Replace x and y
3(-5%2F7) + 4(16%2F7) = 7
-15%2F7 + 64%2F7 = 7
49%2F7 = 7
7 = 7; confirms our solutions,
:
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