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 ~ ~ ~