# Thread: Need Help With Simultaneous Equations by Substitution

1. ## Need Help With Simultaneous Equations by Substitution

Hi, my name is, Carissa. I'm 14 years old and I'm pretty confused about how to solve simultaneous equations by substitution.

Could someone please walk me through it?

2. Originally Posted by Carissa
Hi, my name is, Carissa. I'm 14 years old and I'm pretty confused about how to solve simultaneous equations by substitution.

Could someone please walk me through it?
please post a specific problem that is giving you difficulty.

3. Originally Posted by Carissa
Hi, my name is, Carissa. I'm 14 years old and I'm pretty confused about how to solve simultaneous equations by substitution.
Could someone please walk me through it?
First, let me say that you write extremely well for your age, Carissa.

Say you have these 2 equations:
2x + y = 7 [1]
x + 2y = 8 [2]

From [1], we have y = 7 - 2x ; still with me?

Now "substitute" that in [2]:
x + 2(7 - 2x) = 8
So:
x + 14 - 4x = 8
x - 4x = 8 - 14
-3x = -6
x = -6/-3
x = 2 : OK?

Now "substitute" that in one of the 2 equations; pick [1]:
2x + y = 7
2(2) + y = 7
4 + y = 7
y = 7 - 4
y = 3

...and that's solving by "substitution" ; kapish?