What fraction when added to 1 quarter yields 7 over 9?

The lowest common denominator is 1/4 x 1/9 = 1/36. 1/4 = 36/4x1 x 1/36 = 9/36 7/9 = 36/9x7 x 1/36 = 28/36 28/36 - 9/36 = 21/36 = 7/12