25/28 - (1/9 + 13/28) = 25/28 - (28/252 + 13/28)= 25/28 - (28 + 39)/252= 25/28 - 67/252= (259)/(289) - 67/252= 225/252 - 67/252= (225 - 67)/252= 158/252= 79/126
Therefore, 25/28 - (1/9 + 13/28) = 79/126.
25/28 - (1/9 + 13/28) = 25/28 - (28/252 + 13/28)
= 25/28 - (28 + 39)/252
= 25/28 - 67/252
= (259)/(289) - 67/252
= 225/252 - 67/252
= (225 - 67)/252
= 158/252
= 79/126
Therefore, 25/28 - (1/9 + 13/28) = 79/126.