Five liters of plum juice contains 12% sugar, and two liters of strawberry

Five liters of plum juice contains 12% sugar, and two liters of strawberry juice contains 19%. Juices mixed, how much sugar will the mixture of these juices contain?

According to the condition of the problem, five liters of plum juice contains 12% sugar, therefore, in a given amount of plum juice, sugar occupies a volume equal to:
(12/100) * 5 = 0.12 * 5 = 0.6 l.
It is also known that two liters of strawberry juice contain 19% sugar, therefore, in a given amount of strawberry juice, sugar occupies a volume equal to:
(19/100) * 2 = 0.19 * 2 = 0.38 l.
After mixing the two juices, you get 7 liters of the mixture, in which the sugar will occupy a volume equal to:
0.6 + 0.28 = 0.98,
which as a percentage is:
100 * 0.98 / 7 = 98/7 = 14.

Answer: The juice mixture contains 14% sugar.