Solution: It takes X days to set up a team to do it alone, and then the equations can be listed.

10/X+ 18/24= 1

Solution:

X=40

Prove to be the root of the original equation.

If it takes Y days for Team B to finish it alone, you can list the equations.

10/Y+ 1/40 = 1/24

Solution:

X=60

Prove to be the root of the original equation.

The construction cost of forming team B on Z day is not more than 220,000 yuan. At this time, Party A will have 40*( 1-Z/60).

0.35 * Z+0.6 * 40 *( 1-Z/60)≤22

0.35Z+24-0.4Z≤22

Solution:

Z≥40

Therefore, Team B has to work for at least 40 days.