Question 1138822
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By the Pythagorean Theorem,<br>
{{{(x)^2+(x+3)^2 = 15^2}}}<br>
Solving for x is relatively easy.<br>
But a person with a little experience, seeing that the hypotenuse of a right triangle is 15, will immediately suspect the triangle has side lengths 9, 12, and 15 (3 times the basic Pythagorean Triple 3, 4, 5).  And indeed 12 is 3 more than 9, so the other two sides of the pennant are 9 feet and 12 feet.