To find the mode you need to put all the numbers given in order, then count them and decide which number occurs the most.
Given the number you have here, we're going to put them in order, like so,
78, 78, 83, 85, 89, 91, 95, 98 (they were in order already)
Now we see which number occurs the most.
The number would be 78
~Hope this helped!
Should be 13 weeks. $336-$128= $208
$208/$16= 13 weeks
800 divided by 19
is 42 with remainder 2
= 42 R 2
= 42 2/19