1m is equal to 100cm, so the scale reduces the size of the actual object
So he worked 30.5 hours, he just didn't write some of the hours down. To find the hours he didn't write down, you subtract 8+

+

from 30.5, which equals
Ik but learn its simple but there is multiple answers
Check the picture below.
so, hmmm notice, since i² = -1 and i⁴ = 1, whenever the exponent is only divisible by 2, the value will be -1, and whenever the exponent is divisible by 4, we end up with a +1, so every subsequent even exponent is simply cancelling the previous value, if we take that to the even value of 100, which has 50 pairs of those, we end up with, yeap, you guessed it, 0.
11 + 5 x 4a
Hope this helps! Do you need an explanation?