9. In order to find the area of each wall, let's set it as x,

According to "each first-class mechanic paints more walls 10 square meter than the second-class mechanic", the workload of the first-class mechanic paints more walls 10 square meter than that of the second-class mechanic, and an equal relationship can be established from this sentence.

First-class daily workload = first-class daily workload+10 square meter.

Then how do you find out the workload of both?

Three first-class technicians painted eight rooms a day, but 50m^2 was not painted. From this sentence, list the workload of the first-class technician in one day:

Brush 8 rooms a day at one level, each room is x square meters, those 8 rooms are 8 square meters, 50 square meters are not brushed, that * * * brushes 8-50 square meters, and these three people brush 8-50 square meters. Divided by 3, it is the workload of each level.

Based on this speculation, the workload of each second-level mechanic can also be calculated.

Workload of each first-class mechanic: 8x-50.

———— (This is equivalent to the dividing line)

three

Workload per person of Grade II Technician: 10x+40

—————

five

Their workload difference is 10 square meter.

The general equation is:

8x-50 10x+40

—————=———— + 10

3 5

The solution is x=52.