【Answer】 64
【Solution】Move the blue square to the position in the lower left figure. Since the blue square exactly blocks the red square, and the red square exactly blocks the yellow square, the exposed parts of the red and yellow squares must be equal. The sum of the exposed areas of the red and yellow parts is $19+11=30$, which is divided into two equal parts, each being 15. From the lower right figure, we know that the side length of the blue square is 5, so the width of the red rectangle is $15 \div 5=3$. Therefore, the side length of the large square box is $5+3=8$, and the area is 64.
9. As shown in the figure, three square pieces of paper in red, yellow, and blue of the same size are placed in a larger square box. It is known that among the exposed parts, the blue area is 25, the red area is 19, and the yellow area is 11. The area of the larger square box is $\qquad$. (Provided by Wang Xiaohan, Online School Teacher)

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