Move character by X units on the left

[Schmeep]

if (Input.GetKey(KeyCode.D) && tr.position == pos)
{
pos += Vector3.right;
}
else if (Input.GetKey(KeyCode.A) && tr.position == pos)
{
pos += Vector3.left;
}

[dan_wipf]

instead of vector3.left you can use

new Vector3(1.25f,0,0);