Simplify the following expression by combining like terms:

3x+y+2z−5x−3x−7y

The simplified expression is: -5x - 6y + 2z.

To simplify the expression 3x + y + 2z - 5x - 3x - 7y, you can combine like terms by adding or subtracting their coefficients.

First, let's combine the x terms:
3x - 5x - 3x = (3 - 5 - 3)x = -5x

Next, let's combine the y terms:
y - 7y = (1 - 7)y = -6y

Now, let's rewrite the expression with the simplified terms:
-5x - 6y + 2z