Answer
There are approximately 19 neutrons left over.
Work Step by Step
From Figure 42-5, we can see that a nucleus with 39 protons has approximately 50 neutrons.
From Figure 42-5, we can see that a nucleus with 53 protons has approximately 74 neutrons.
These two nuclei have a total of approximately 124 neutrons.
$^{235}U$ has 92 protons and 143 neutrons.
We can find the number of neutrons that are left over:
$143 - 124 = 19$
There are approximately 19 neutrons left over.
