m= 1000-6-82-256-220=436，

n=436 1000=0.436，N=220 1000=0.220。

The histogram of frequency distribution is shown in the following figure:

(2) Let X be the number of people with 90 points or above in liberal arts mathematics in the city.

Then 100020000 = 656x, and x =13120;

(3) Let four boys be represented as A 1, A2, A3, A4,

Three female students are marked as B 1, B2,

The basic events of recruiting 2 students from 6 students are:

(A 1，A2)，(A 1，A3)，(A 1，A4)，(A 1，B 1)，(A 1，B2)、

(A2，A3)，(A2，A4)，(A2，B 1)，(A2，B2)，(A3，A4)，

(A3, B 1), (A3, B2), (A4, B 1), (A4, B2), (B 1, B2), * * 15.

We take "there are 1 girls in 2 people" as event A, and there are:

(A 1，B 1)，(A 1，B2)，(A2，B 1)，(A2，B2)，(A3，B 1)，(A3，B2)，(A4，B 1)，(A4，B2)，

***8 kinds, so 2 out of 6 people are admitted, and the probability that 1 is a girl is 8 15.