Part A:
Let's focus on the following two lines of Jillian's procedure:
[tex]7+3\cdot16,[/tex][tex]10\cdot16.[/tex]
As we can see, she added the 3 and the 7. However, in an arithmetic operation the multiplication takes priority over the addition, and as a result she should have multiplied the 3 and the 16 first before doing the addition.
Part B:
Let's work on simplifying the expression in a similar manner as it was done in the example:
[tex]7+3\cdot(10-6)^2,[/tex][tex]7+3\cdot(4)^2,[/tex][tex]7+3\cdot16.[/tex]
Now, because of the PEMDAS criteria, we do the multiplication first:
[tex]7+48,[/tex][tex]55[/tex]
