Answer:
1) If you want to know what percent is X in Y, you must do:
X/Y*100%
so in this case:
(2/3)/(1/4)*100% = 266.66%
So 2/3 is the 266.66% of 1/4
and
(2/3)/(1/6)*100% = 400%
So 2/3 is the 400% of 1/6
2) We have 18kg of black tea, and each kg cost $3.5
we want to mix it with X kg of green tea, (with a cost of $2.6) so the total cost per kg is $2.9
The final weight of the mixture will be 18kg + X
and the price of the each kilogram in the mixture will be:
P = (18kg*3.5 + X*%2.6)/(18kg + X) = $2.9
we must solve it for X
(18kg*3.5 + X*$2.6) = $2.9*(18kg + X) = $2.9*18kg + $2.9*X
X*($2.9 - $2.6) = ($3.5 - $2.9)*18kg
X = (0.6/0.3)*18kg = 36kg
So you need to add 36kg of green tea.