Solution: If the gas price of 20 10 is X yuan, then 2011(1+25%) is X yuan.

96/x-90/( 1+25%)x = 10

96 * 1.25-90 = 10 * 1.25 x

12.5x=30

x=2.4

Then (1+25%)x=2.4*25%=3 (yuan)

Answer: 20 1 1 The price of residential gas in this city is 3 yuan.