The community garden is a rectangle, 60 meters long and 40 meters wide. Now we should plant trees around the garden. At all four corners, every two adjacent trees are 5m apart, and one * * *, 40 trees should be planted.

The specific answer is as follows:

60÷5×2+40÷5×2

= 12×2+8x2

=24+ 16

=40

So a * * * should plant 40 trees.

Mixed operation:

If the first-level operation and the second-level operation exist at the same time, the second-level operation is calculated first. If there are one, two and three operations at the same time (i.e. power, root and logarithm operations), the third operation is calculated first, and then the other two levels are calculated.

If there are brackets, count the numbers in brackets first (no matter what level, count first) The third level should be counted in brackets, and then the second and first levels should be counted.