1. The problem has X channel, the easy problem has Y channel, and the medium problem has Z channel. According to the meaning of the question,

Equation set

x+y+z= 100

①

x+3y+2z= 180

②

①*2-②,

That is 2x+2y+2z-(x+3y+2z).

x-y=20，

2. Let 100 have x difficult questions and y simple questions. Then the medium title is (100-x-y) road.

According to the topic:

x+2( 100-x-y)+3y=60×3

Because only one person solved the difficult problem, two people solved the medium problem and three people solved the simple problem. Three people always * * * solve 60×3 problems, and repetition counts)

Get by solving the equation

y-x=-20

that is

x-y=20

X-y= difficult problem-simple problem =20

Get 20 questions that are more difficult than simple questions.

That's how it should be. I don't know if it's right. . . .

I didn't seem to make myself clear. I don't know if I understand ~ ~ ~