Hello,
I suppose a and b are vectors
and i and j unit's vectors

I you think about it 12a with the 2 on the rope is actually 144 because it’s multiplied by 12 so maybe that helps?
(4+8/2)*5-1
first step divide in the parentheses
(4+4)*5-1
second step add in the parentheses
8*5-1
third step multiply
40-1
last step subtract
39
If she flipped the coin 50 times and it was tail 27 you would time 27 by 4 and it would equal 108 because 50 times 4 is 200