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How to do the second and third questions on page 29 of the first volume of the third grade mathematics of Beijing Normal University Edition?
2. Let the total number be x, (1/8x) 2+12 = x;
1/64x^2-x+ 12=0；
1/64(x-32)^2=4；
x = 16；
3. If the height is x, the width is15/x;
The AEF area of the triangle is15/x * (8-x)/2;
The area of triangle BGE+ triangle CFH is (10-15/x) * x/2;