A=1/2h(b1+b2) is the formula for the area of a a trapezoid b regular polygon c triangle d rhombus or kite

answer:  

\boxed {\frac{1}{5}}  

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solution-

60 *   \frac{1}{5}   = 12

90 * \frac{1}{5} = 18

75 * \frac{1}{5} = 15

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hence, the answer would be \boxed {\frac{1}{5}}