Insert parentheses and or additions sings to make equation true 3 2 4 1 = 13

One way could be:

(3 * 4) + 2 - 1

Parentheses indicate multiplication (no need to use the "*" sign).

So the question is basically asking for the usage of multiplication and addition only.

To get 13 through the given combination using only parentheses and addition, you can write it as follows:

3 + 2 (4+1) = 13

Now, let's check this:

3 + 2 (4+1)

= 3 + 2 (5)

= 3 + 10

= 13 which is the required output.