Question 14393
{{{(3a-12b+c)-(6a+20b-3c)}}}
{{{3a-12b+c-6a-20b+3c}}}
{{{3a-8b+4c}}}
Why did you subtract the -12b and the -20b?
You need to remember they are both negative numbers, so you will actually add them and keep the negative sign.
=)