So, Using your conversion chart(if you have one) you'd see 1 liter makes 1000 milliliters. So, if you have half of a liter(0.5), then you have 500 milliliters. If he adds 300 more, then you get 800 milliliters total, which is also equal to 0.8 liters. Hope this helps!
About 20 it depends on how big the termite is.
Here it goes:
a. Because you have four blue marbles out of the 12 total marbles, the probability is 4/12. YOU MUST SIMPLIFY down to 1/3.
b. There are 12 marbles in the bag right now, and the probability is 4/12, you must add some marbles. 1/10 multiplied by 4 is 4/40. There are 4 blue marbles right now, and 40 minus the 12 there are right now is 38, so you would need to add 38 non-blue marbles.
