So,
For every 2 large notebooks Ann orders, she orders 1 small notebook.
This can be stated as a ratio: 2:1
Add up the units to find the value of each unit.
2 + 1 = 3
Divide 48 by 3 to get the unit value.
48/3 = 16
The unit value is 16.
The number of large notebooks Ann orders is 2(16):16
This is a 2:1 ratio.
Therefore, Ann ordered 32 large notebooks and 16 small notebooks.
You asked to find what price, given ...
... $6.40 = 4% × (what price)
Divide by 4%
... $6.40/0.04 = (what price) = $160.00 . . . . matches selection D)
395/1000 will reduce down too 79/200