a. We're looking for
such that




b. Integrating with respect to
will make things easier.

(where we take the positive square root because we know
)
Now we want to find
such that




Levant will receive about 9 american dollars when he exchanges his pesos.
According to this question, 1 american dollar is worth about 11 pesos. In order to find that, you need to divide 3000/270 which gives you around 11. In order to find out how many dollars he will receive for his pesos, you need to divide 100 by 11 which gives you about 9 dollars.
As the key suggests, the left part is the integer part of the number, while the digit on the right is the decimal part of the number.
So, for example, the first row describes the two values 97.2 and 97.8, while the second row describes the values 98.1, 98.3 (repeated twice), 98.5, 98.6 and 98.7 (repeater three times).
So, the number of values is given by the number of leaves: you simply have to count how many digits are there on the right part of the screen.
The answer is thus 24