How do I simplify this algebraic expression 3x+2a-4x

Start by changing the - 4x to + - 4x.

So we have 3x + 2a + - 4x.

To simplify, we can only combine what are called our like terms and in this problem, we have a pair of like terms in our x terms.

3x + - 4x simplifies to - x.

So our answer is - x + 2a.

Note that if you wrote your answer as - 1x + 2a, it means the same thing. However, as we move farther into math, we usually tend to drop the - 1 or 1 that is in front of a variable since it's implied