A friend of mine taught remedial algebra at the University of Washington. She related to me that if she wrote on the board:

    x + 3 = 5

and asked what `x` was, the students would fall over in a quivering heap and say they had no idea.

If, instead, she wrote:

    _ + 3 = 5

and asked them to fill in the _, they all had no difficulty with it. The problem was not that they couldn't grasp the concept, it was that at some point they latched onto the notion that algebra was hard, and `x` meant algebra, and that was the end of that.

Thank you!

Agreed, Abstraction for example, is really really hard for most people, like harder than most technical folks realize.