1, let the monthly water consumption of each household be x, and the water fee should be y yuan. Write the relationship between y and x:
[1], when x is less than 20 cubic meters or y is less than 68 yuan:
3.4*x=y，y/3.4=x
[2] When X is greater than 20 cubic meters or Y is greater than 68 yuan:
20*3.4+[x-20]*4.2=y，[y-68]/4.2+20=x
2. If the water consumption is 20 cubic meters per month, how much should I pay? ：
3.4*20=68 yuan
Xiao Ming's water fee payment in the second quarter is as follows. 55.76 yuan in April, 72.2 yuan in May and 6 1.88 yuan in June. How many cubic meters of water is used this season? ：
According to [2], 68 yuan can be set as the base. If it is less than or equal to 68 yuan, the unit price can be divided into direct quantities and the amount calculated by 68 yuan:
[55.76+68+61.88]/3.4+[72.2-68]/4.2 = 54.6+1= 55.6 tons or cubic meters.