Question

Dallas solved the system of equations below. What mistake did he make in his work?
3x + y = 6
x − 2y = 2

y = 6 − 3x
x − 2(6 − 3x) = 2
x − 12 + 6x = 2
5x − 12 = 2
+12 +12

x = 2.8

3(2.8) + y = 6
8.4 + y = 6
−8.4 −8.4
y = −2.4

He should have substituted 6 + 3x.

He combined like terms incorrectly. It should have been 7x instead of 5x.

He made a mistake in distributing −2.

He made no mistake.

Answer 1

so have you noticed anything wrong?

Answer 2

$$
y = 6 − 3x\\
x − 2(6 − 3x) = 2\\
\color{red}{x} − 12 + \color{red}{6x} = 2\\
\color{red}{5x} − 12 = 2\\
+12 +12\\
\\
x = 2.8
$$
so, what do you think?

Answer 3

thanks

Answer 4

yw