Tasha says that the expression 6.8w-4.7 can be simplified as 2.1w. Her teacher explains that this is not correct. What mistake did Tasha make

Answer: She combined unlike terms.

Step-by-step explanation:

You can only combine like terms. If a number has a variable, you must make sure that the number you're operating it with has the same variable raised to the same power (if applicable)

6.8w-4.7 is in its simplest form.

To be able to subtract these, 4.7 must have a ''w'' variable as follows;

6.8w-4.7w=2.1w