In order for the total displacement to be zero, the amount of forward displacement must be equal and opposite to the amount of backward displacement. Since the steps are the same length, they must be equal in number.
Half of the 10 steps were forward, and the other half were backward.
5 steps forward; 5 steps backward.
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<em>Additional comment</em>
Math develops from an effort to model the real world. It would probably give you some insight into this problem if you were to physically take some steps to see how many forward and backward you would need to end where you start.
