Since she decorating 45 cookies
Since she decorates 1/3 of them with pink sprinkles
Let us find 1/3 of 45

Then the remaining = 45 - 15
The remaining cookies = 30
Since she decorates 2/5 of the remaining with heart sprinkles
Let us find 2/5 of 30

Then the rest = 30 - 12
The rest = 18
She decorates 18 cookies with blue sprinkles