Can you please go step by step, Ill show what I did and you can correct me.

The question is:
a+a(x+1)

My way:

a+a(x+1)
2a(x+1)
2ax+2a

Could someone please check over this and provide a correct answer and my error.

Thanks in advance.

a+a(x+1) does not equal 2a(x+1)

If it was (a+a)(x+1), then that would work, but it's not.

The correct next step is:
a+a(x+1)=a+ax+a

Thank-you

You may not add the terms a and a(x+1) since they are not the same. You can add a and a or a(x+1) and a(x+1) but not the in-between.
Firt, expand the second term by multiplying each term withing the parentheses by a.
a+a(x+1)=
a + ax + a =
then you may add the same terms to obtain:
2a + ax =
I don't know where you are going with this equation or the final form in which it is to be found; however, you can now factor out a to obtain
a(2+x). That is how I would leave it.

Let's go through the steps again to find the correct answer.

Original expression: a + a(x + 1)

Step 1: Distribute the a to every term inside the parentheses.
a + ax + a

Step 2: Combine like terms, grouping the terms with the same variables together.
2a + ax

So the correct answer is 2a + ax.

Your error was in step 2, where you attempted to simplify the expression by combining a and a(x + 1) into 2a(x + 1). However, since a and a(x + 1) are not like terms, they cannot be combined in this way. Instead, we combine the two a terms in step 2 to get 2a, and the ax term remains unchanged.