China Naming Network - Eight-character query< - Half of the students do math, one quarter draw pictures, one seventh read little English and one seventh play on the playground. How many people have a process?
Half of the students do math, one quarter draw pictures, one seventh read little English and one seventh play on the playground. How many people have a process?
1、 1- 1/2- 1/4- 1/7=3/28
Therefore, the minimum number of personnel =3/(3/28)=28 (people); Maximum value =6/(3/28)=56 (person)
2、
3x-5y=2a……( 1)
2x+7y=a- 18……(2)
Substituting x=-y into (1)(2) gives: x = a/4 = (18-a)/5; y=-a/4=(a- 18)/5
Get: 5a=4( 18-a)，get: a=8。
Then: x=a/4=2, y=-x=-2.