Ok. So since we do not know the total he starts with, we can use a variable.
x is his first amount.
Then he pays the babysitter 12 dollars an hr for 4 hours.
12*4 = 48
so x-48
x-48
Now, his wife gives him $10
-48+10 = -38
The amount in his wallet changes by -38. Therefore, he loses 38 dollars.