Here is an example of to solve a two step algebraic equation.

3x+ 6 = 15

The blue is the coefficient.
The green is the variable.
the red is the constant.
the pink is the answer.

First you have to isolate the constant by doing the opposite to each side to balance it out. so in this equation in order to isolate the constant which is positive six you have to put a negative six beside it and to balance it out you have to put a negative six beside the answer as well. 

3x +6 - 6 = 15 - 6

Then you have to solve the part that is highlighted. You have to subtract positive six by six and the answer is zero. because the answer is zero you don't have to write it because it wont make a difference. then after that you have to subtract positive fifteen by six and the answer is positive nine. and then you re write the question.

3x +6 - 6 = 15 - 6
3x = 9

After rewriting the question in order to get the answer you must divide three x by three and nine by three to balance it out. and now all you have to do is solve one step algebraic equation.

3x +6 - 6 = 15 - 6
3x = 9
3x = 9
3      3

After that you have to divide three x by three and nine by three. in order to get the answer you have to divide three by three and the answer is one but you don't have to write that because there already is a one beside the variable it is just not written there because it is not needed so you just write x equals. and then after that you have to divide nine by three and the answer is three so you write down three.

3x +6 - 6 = 15 - 6
3x = 9
3x = 9
3      3
x = 3