If x is the third proportion to a and b, then a:b = b:x. 9/12 = 12/x => 9x = 144 => x = 16.
यदि x, a और b का तीसरा समानुपाती है, तो a:b = b:x। 9/12 = 12/x => 9x = 144 => x = 16।