It is known that a=2*3*m, b=3*5*m, the greatest common factor of a and b is 15, then m=how much.
已知a=2*3*m，b=3*5*m，a和b的最大公因数是15，则m=多少．
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>