Solution: (1) Suppose there are x cars with 45 seats for rent, then there are (x- 1) cars with 60 seats. According to the equal number of people, the formula can be as follows:

45x=60(x- 1)-30

15x=90

x=6

45x=45*6=270 (person)

That is, the number of people participating in the spring outing is 270.

(2) Assume that X 45-seat buses are rented, and the rented 60-seat buses are (x+ 1).

45x+60(x+ 1)=270

x=2

X+ 1=3 (vehicle)

That is, two 45-seat buses and three 60-seat buses were rented.

The required rent is: 250*2+300*3= 1400 yuan.