It is known that the lengths a, b, and c of the three sides of a triangle are all integers, and a≤b≤c, if b=7, how many such triangles are there?
已知三角形的三边的长a、b、c都是整数，且a≤b≤c，若b=7，则这样的三角形有多少个．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">7 * 8</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>