2x + y = 5
x − 2y = 10
y = 5 − 2x
x − 2(5 − 2x) = 10
x − 10 + 4x = 10
5x − 10 = 10
<em>add 10 to each side</em>
<em>5x-10+10 = 10 + 10</em>
<em>5x=20</em>
5x = 0 <em>this is the error</em>
He needs to add 10 to each side
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Given:
1. AB = 3x +2; BC = 4x + 8; AC = 38
2. AB + BC = AC incorrect (not an angle angle addition postulate)
3. 3x+2 + 4x + 8 = 38 correct
4. 7x + 10 = 38 correct
5. 7x = 28 correct
6. x = 4
Daniel made an error on line 2.
