Suppose that only 1 person has the number of problems solved by X, 2 people have the number of problems solved by Y, and 3 people have the number of problems solved by Z,

Then three people * * * to solve the problem is:

x + 2y + 3z = 60* 3.....................( 1)

Excluding the repeated parts, three people worked out the following questions:

x + y + z = 100............................(2)

(2)*2-( 1) Available:

x - z = 20，

That is to say,

There are 20 more difficult questions than easy ones.