1 If you are busy, I will leave you alone.
If you were busy, I would leave you alone
If you had been busy , I would have left you alone.
2 If I get a ticket, I will go to the Philharmonic.
If I got a ticket, I would go to the Philharmonic.
I I had got a ticket, I would have gone to the Philharmonic.
3 If we receive a telegram from him, we won't worry.
If we received a telegram from him, we wouldn't worry.
If we had received a telegram from him, we wouldn't have worried.
4 If he lives in Moscow, he will visit the Tretyakov Gallery every year.
If he lived in Moscow, he would visit the Treatyakov Gallery every year
If he had lived in Moscow, he would have visited the Tretyakov Gallery every year.
5 If you don't work systematically, you will fail at the examination.
If you didn't work systematically, you would fail at the examination.
If you hadn't worked systematically, you would have failed at the examination.