10 x 62 is the equation for this problem because every row has 62 and there are 10 rows.
First find how much you've had. Make the fractions with similar denominaters: 1/3(2)=2/6, 1/2(3)=3/6, 5/6(1)=5/6. Now add the fractions: 2/6+3/6+5/6=10/6 or 1 4/6 or 1 2/3. Then add the whole numbers: 10+15+20+1=46. So you've had 46 2/3 oz now subtract that from how much you need: 64-46 2/3= 63 3/3-46 2/3=17 1/3. You still need 17 1/3 water :)
I know you got this from Khan Academy, and so the answer is $9.81. You probably don't care about how it is done, and you probably just want to put the answer and be done, but I will show you. You have to take the original price of $9 and multiply it with 9%, or 0.09, to get the amount of your tip. add the 9%, or $81. You can also just do 9*109%, or 9*1.09, to put these two steps together and add the original price and the tip.
