Answer:
He made a mistake in his calculations when simplifying 5x - 2y
Explanation:
Given
The coordinate pair

The equations


Dimitri's Solution








Required
Identify Dimitri’s mistake
In the first equation, Dimitri made no mistake.
However, he made a mistake when simplifying the second equation.
We have:

and

Substitute
and

So, we have:

Open bracket

Finally, we have:
