In order to add or subtract fractions they must have a common denominator.
to get a common denominator you need to multiply fraction 15/32 by 45 and multiply fraction 11/45 by 32
45(15/32) - 32(11/45)
675/1440 - 352/1440
now you subtract the numerators and keep the denominator the same and you should get
323/1440 as your answer.