Теорія:

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?
  
drinking-water.jpg

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.
  
quit-my-job.jpg

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?
  
bigstock-Surprised-Beauty-6228700.jpg

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.
Джерела:
bodiesofwater.solutions
www.startofhappiness.com
popista.com