# algebra

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Solving Systems by Substitution:

2. x=1-4y
2x+7y=3

I need help learning how to do this problem step-by-step

• algebra -

x = 1-4y

so "substitute" 1-4y wherever you see x in the other equation

2x+7y=3
2(1-4y) + 7y = 3
2 - 8y + 7y = 3
-y = 1
y = -1

next sub that y = -1 back into the first equation
x = 1 - 4(-1) = 1+4 = 5

• algebra -

x = 1-4y
2x+7y=3

Starting with the first equation
since x = 1 - 4y

Plug that in to the second equation

2(1-4y)+7y=3
2 -8y + 7y = 3
2 - y = 3
2/2 - y = 3/2
- y = 3/2

Since why can't be negative, move the negative over to the other side

y = -3/2
Okay we found what Y is now plug that into the first equation

x = 1-4(-3/2)
x = 1 + 6
x = 7

I'm pretty sure this is right, but I hope a real tutor comes and say for sure

• algebra -

Oh sorry, I did my math wrong and Divided instead of subtracting.

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