The answers to questions 5, 6, 7 and 8 on page 5 of the seventh grade math book.

5. if it takes x days to manufacture part a, it takes (30-X) days to manufacture part b:

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.