Answer:
336
Explanation:
If 42% said they shopped online last week, that means the number of people who said they shopped online last week is 42% of 800. "Of" just means we should multiply, and since 42% = 42/100 (since % is just /100), we can use the following to find the answer (I used cross multiplication to simplify):
42 800 42 8
--- * = ---- * = 336
100 1