Solution: Set air conditioner X yuan and electric fan Y yuan.

It is known that 8 sets of air and 20 sets of electricity need 17400 yuan, and 30 sets of air need 22500 yuan.

Then 8X+20Y= 17400 ①

10X+30Y=22500 ②

① Formula X3 gives 24X+60Y=52200 ③.

② Formula X2 gives 20X+60Y=45000 ④.

Then ③-④ can get 4X=7200 X= 1800 and substitute Y= 150.

Answer: empty ... each set 1800 yuan ... each set 150 yuan.

the second question ..

Solution: empty .. X group power .. Y group.

From the title, we can see that ...

X+Y=70

1800X+ 150Y≤30000

200X+30Y≥3500

Available X= 1 1 Y=59.

Answer: empty ... enter 1 1, and electricity ... to enter 59.