About single player missions, how do I accomplish level 28, Arrow Head?

Level 28 on single player missions also called arrow head, can easily be destroyed by using air attack.
You will need 5 dragons or 12 or 16 balloons.
Either set can do the job for you.
Also bring three lightning spells with you.
Use the lightning spell to destroy the single air defense in the middle.
Then drop one dragon on each archer towers on both sides and one on the hidden teslas located on the upper left part.
Any level of dragon can do this task for you very easily.
If you want to use lower cost troops, then you can use the balloons instead.
Same principle applies.
Drop two or three balloons in place of the dragon.
Once the archer towers and the hidden teslas are destroyed, no other defensive buildings can target your troops.