Answer:
if you meant x times y...
15 x 20 is 300.
if you meant x + y...
15 + 20 is 35.
if you meant anything else, please let me know
the way it was written confused me but I tried.
The average of those two values is
(-11-4 +i+4i)/2 = -(15/2) +(5/2)i
It would be: 41/16.4 * 100 = 4100/16.4 = 250%
The easiest way to do this would be to imagine that Jolie has 100 marbles. If Mary has 40% fewer, that means she has 60 marbles. Then if they combine all their marbles into a single bag, they will have 160 marbles, of which 100 are Jolie's. So the % that is Jolie's is 100/160 = 0.625 = 62.5%.
Question: What is 16% of 80?
You have to change the percentage to a decimal.
Remove the percentage sign and divide by 100 (% are based off 100)
16%⇒.16
Now multiply .16 and 80

Answer: 12.8