Answer:
John got 94 marks
Step-by-step explanation:
average = total numbers/ no. of students
77= x/16--------------1
78=x+y/17------------2
From 1 : x= 77*16= 1232--------------3
From 2: x+y= 78*17= 1326---------4
subtracting 3 from 4
y= 1326-1232= 94
12 bow ties
1/2 yard = 1.5 feet = 1 bow tie
1.5 x 2 = 3 feet
1 yd = 2 bow ties
18/3 = 6 yards
6 x 2 = 12 bow ties
D
See attached image.
