Your answer is D because 10*2 is 20 and 6*2 is 12 so 12 out of the next 20 customers will purchase a sandwich.
I'm attaching the solution.. feel free to ask if you have questions.. I basically did long division. Hope this helps.
(You go from left to right)
(Dividend is 931, divisor is 7)
Step 1: Look for a number smaller than 9 that is divisible by 7. 7 is the only one which is smaller than 9 and is divisible by 7. Now that you know 7*1=7, you put 1 above 931 (Dividend)
Step 2: You subtract that number from the number in tens place. And bring the leftover down.
Step 3: You repeat Step 1 and 2 until either you get a remainder of 0 or the remainder in smaller than the divisor (in this case 7)
(Therefore 931/7=133, quotient=133, remainder=0)
^Hope this helps.
Posting screenshot of my answer in the linked question in case it gets deleted.
Answer:
(A)74
Explanation:
Let her average score on the last two tests = x.
The six scores will now be: 82,78,87,73, x and x.
Since the average score for her first six chemistry tests = 78

We then solve for x.

Her average score for the last two tests is 74.