Verified answer

解ります means can solve something.

分かりますmeans understand o know something.

1.「Ａ君が何を言いたいのかワカらない」

I can not get what A(person) mean.

2.「最近は男か女かワカらない若者が多い」

In these days ,there are a lot of youn poople I can not tell

whether they are boys or girls

3.「Ｂ君が旅行へ一緒に行かない理由がワカらない」

I can not understand why B(person) will not go to travel together

You can use "分かる"　and　"分からない"　in　all　cases

(in modern use)

but originally

解る、解らない　were used for 1

判る、判らない　were used for 2

分かる、分からない　were used for 3

but　originally