For a, b, c, d to be in proportion, a/b = c/d. So 12/18 = 20/d => d = (18 * 20) / 12 = 360 / 12 = 30.
a, b, c, d के समानुपात में होने के लिए, a/b = c/d। इसलिए 12/18 = 20/d => d = (18 * 20) / 12 = 360 / 12 = 30।