Answer:
The answer is A.
Step-by-step explanation:
Given that Winnona took 5 tests and retake Test 5. So the mean score for this question is Total number of scores divide by Total number of tests is equals to 87 :
Let Test 5's score be x,
Let mean score be 87,

Next you have to solve the value of x :

Yes, it is very important otherwise some teachers may count the problem wrong.
Adding more short sentences.
The ratio is 9 : 7 which means for every 9 pounds of Quartz you have 7 pounds Marble. For the second row Quartz is 72. For the third row it's 11 bags because 99/9 = 11 and 11 times 7 equals 77. The four one is 126 pounds Quartz. Finally the last one is 15 bags and 15 times 7 is 75 pounds of Marble. What you do with the ratio is multiply by the number of bags to figure out with this many bags how many Quartz or Marble. You can do the same thing to figure out how many bags.