Study the information about adjective + to.
1. Adjective + the infinitive (to)
Use this structure with adjectives: difficult, easy, hard, impossible, dangerous, safe, expensive, cheap, nice, good, interesting, exciting.
Do you think it is safe to drink this water?
It is interesting to play with Jim.
2. It is nice of you to...
You can use many other adjectives: kind, sensible, sad, amazed, careless, unfair, considerate, silly.
It is silly of Mary to give up her job when she really needs money.
3. I am sorry to/I was surprised to…
Use the structure adjective + to if you want to say how somebody reacts to something.
Other adjectives for this purpose: happy, lad, pleased, sad, disappointed, surprised, amazed, astonished, relieved.
Was Mary surprised to see you?
4. Use to after the first, the last, the next, the only, the second.
He is the first to orbit the Earth.
5. Something is sure/certain/likely/bound to happen.
Jim is a good student. He’s bound to pass this test.