Final answer:
Sally can use the proportion 165/100 = w/340 to find out what number is 165% of 340. After setting up this proportion, she can cross-multiply and divide to solve for the unknown number w.
Step-by-step explanation:
To find out what number 165% of 340 is, Sally can set up a proportion where the percentage is compared to 100 and the unknown number (represented by w) is compared to the original number. Therefore, the correct proportion Sally can use is C. 165/100 = w/340. This is because 165% expressed as a ratio is 165/100, and we are comparing this to the ratio of the unknown number w to the original number 340.
To solve for w, Sally would cross-multiply and divide, so the equation would be (165/100) * 340 = w. Sally would be able to find the unknown number by performing these calculations