9514 1404 393
Answer:
it depends on what the question is (no question is given)
Explanation:
What you add or subtract will depend on the problem you're trying to solve, and how you're trying to solve it.
Perimeter
The two left-side vertical segments are 13 and 3. The right-side vertical segment is 16. As you can see, these have the same total: 16.
The top horizontal segment has a length of 21. The two bottom horizontal segments have lengths 16 and 5, for a total of 21—the same as the top segment.
For simple L-shaped figures like this, the overall horizontal lengths and the overall vertical lengths are the same as they would be for a rectangle that is 21 wide and 16 high.
P = 2(L+W) = 2(21+16) = 2(37) = 74 units
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Area
The dashed lines divide this figure into 3 rectangles.
left side: 16 wide by 13 high
upper right: 5 wide by 13 high
lower right: 5 wide by 3 high
You can see that the vertical measures must "add up", as must the horizontal measures. This fact helps you determine the lengths of the unmarked sides.
You can compute the area from the three rectangles identified above, or any of several other ways. One of my favorite is to compute the overall area of the 21 wide by 16 high rectangle, then subtract the 16 wide by 3 high white space at lower left.
area = 21·16 -16·3 = 16·(21 -3) = 16·18 = 288 . . . . square units
Adding the 3 rectangles identified above gives ...
16·13 +5·13 +5·3 = 208 +65 +15 = 288 . . . . same area