500 X = 250(30 X).
X= 10,30-X=20 .
6. It takes X hours to set the topic * * *:
1/7.5+X/5= 1,2/ 15+X/5= 1 .
2+3X= 15 .
X= 13/3 hours.
Question 7 is set by X people and lasts for 2 hours:
2X/80+8(X+5)/80=3/4 .
X= 10 .
Choice of graduate schools:
A, three books (local, school, professional) are the easiest to succeed.
B, three spans (cross-regional, cross-school, cross-professional) are the most difficult to succeed.
C, one book and two spans (this major, cross-regional, cross-school) is the most ideal.
D, two books and one cross (local, professional, cross-school) can be the most successful.
E, two books and one cross (local, school, cross-major) is the best success.