In Pet Rescue Saga Level 740 you need to rescue only 4 pets, but these pets are above some random wooden cages, some of which are also covered in mesh and some with both metal and mesh.
There are unlimited moves to do it in.
The cages that appear in this level are random, sometimes you'll find many of them covered in mesh and metal, other times hardly any.
If when you open the game there are too many mesh/metal covered cages to clear with only the 4 line blasters and 3 bombs provided, don't be afraid to quit and try for a more reasonable board.
This level is mainly a matter of lining up your wooden cages that are covered with metal/mesh to be blasted or bombed.
Plan your moves carefully and it can be done.
Once the metal and mesh are removed and if a wooden cage is empty, the simplest way to destroy it is to just let it smash at the bottom.
Don't worry if a pet does get caught, as long as you blast or bomb the cage before it hits the ground, then the pet will get out.
The easiest way to tackle this level though, is to keep a block between your pets and the cages, and just let them drop.