Correct, True, Right
い adjective
Ending with an い tells you that this word is an い-adjective. So since you know that the kanji 正 means "correct," what is the adjective version of that word? Well, it's also correct.
ただしい
This word uses a reading you didn't learn from the kanji. You have to remember the ただ portion in order to read this word, so think about it this way: After you get the answer correct a clown jumps out of nowhere yelling "Ta-da (ただ)!!!" Imagine it scaring the crap out of you, too.
ママはいつも正しい。
Mom is always right.
ぼくが三日にホテルに入ったというのは正しいです。
It's true that I went into the hotel on the 3rd.
入り口の正しい入り方をおしえてあげましょうか？
Would you like me to show you how to enter an entrance properly?