Solving math problems with equations in Grade Seven Entering the flood season, the students of class 1, Grade 7 went to the reservoir to investigate the flood situation There are 10 flood sluices in total. Now the water level of the reservoir exceeds the safety line, and the river water in the upper reaches still flows by one Constant speed into the reservoir, students after a day of observation and measurement, do the following Record: one sluice gate was opened in the morning, and the water level continued to rise within 2 hours 66km. After opening two sluice gates in the afternoon, the water level dropped by 0.1M in 4 hours. At present, the water level of the sluice gate is lower than that of the sluice gate The water level is still 1.2m above the safety line (1) If five sluice gates are opened, it will take several hours for the water level to drop to the safety line ? (2) If the flood control headquarters requires the water level to drop to the safety line within 6 hours, it should call again How many floodgates are open? Please give me the process thank you The unit of 0.66 is meter

Solving math problems with equations in Grade Seven Entering the flood season, the students of class 1, Grade 7 went to the reservoir to investigate the flood situation There are 10 flood sluices in total. Now the water level of the reservoir exceeds the safety line, and the river water in the upper reaches still flows by one Constant speed into the reservoir, students after a day of observation and measurement, do the following Record: one sluice gate was opened in the morning, and the water level continued to rise within 2 hours 66km. After opening two sluice gates in the afternoon, the water level dropped by 0.1M in 4 hours. At present, the water level of the sluice gate is lower than that of the sluice gate The water level is still 1.2m above the safety line (1) If five sluice gates are opened, it will take several hours for the water level to drop to the safety line ? (2) If the flood control headquarters requires the water level to drop to the safety line within 6 hours, it should call again How many floodgates are open? Please give me the process thank you The unit of 0.66 is meter

Let the upstream water flow into the reservoir x meters per hour, and each sluice can discharge y meters per hour. According to the first condition, that is, in the morning and in the afternoon, we can get two equations: 2x-2y = 0.06 in the morning and 4 * 3y-4x = 0.1 in the afternoon. Note that here we write that two more sluice gates are opened, and a total of three sluice gates are opened