## Elementary Technical Mathematics

$25.6$ ft
The base of the figure is $55.6$ ft long. This length is equal to the sum of the three horizontal line segments on top of the figure. Two of those three horizontal line segments are both $15$ ft long, so their total length is $30$ ft. Thus, the length of the third horizontal line segment, which is labeled $A$, is the difference between $55.6$ ft and $30$ ft. Subtract the numbers (write $30$ as $30.0$) to obtain: \begin{array}{ccc} &&55.6 \\&- &\underline{30.0} \\&&25.6 \end{array}