Answer:
[tex]2.\bar{81}mm[/tex]
Step-by-step explanation:
First the formula for find the are of a trapezoid is:
[tex]A = \frac{h(a+b)}{2}[/tex]
Where [tex]a[/tex] is the top, [tex]h[/tex] the height and [tex]b[/tex] the base measures.
Then we need to know what is the base ([tex]b[/tex]), for that isolate [tex]b[/tex] from the equation
[tex]2A = h(a+b)\\\frac{2A}{h} = a+b\\\frac{2A}{h} - a = b[/tex]
Then in the new equation replace the given values:
[tex]A = 65mm^2\\a = 9mm\\h = 11mm[/tex]
[tex]\frac{2 \cdot 65mm^2}{11mm} -9mm = b\\\frac{130mm^2}{11mm} -9mm = b\\11.\bar{81}mm -9mm = b\\2.\bar{81}mm = b[/tex]
So the final answer is [tex]2.\bar{81}mm[/tex]
