First we add 0.3 to 3.7, that way we will have an integer and it would be more easy to make the operations. Then we have 4.
Then we can substract the 4 to the 9.4, getting 5.4.
Finally we add once again 0.3 (because in the difference we have an extra .3) to the 5.4, getting 5.7.
Then Tamela swims 5.7 more than Blake every day.