Катер по течен реки проходит за 7 часов а против течения за 9 часов. скорость реки 5 км в час. найти собственную скорость катера

Пусть Х - собственная скорость катера. Тогда скорость по течению  Х + 5, а против течения  Х - 5. Получаем уравнение

7 * (Х + 5) = 9 * (Х - 5)

9 * Х - 7 * Х = 45 + 35

Х = 80 / 2 = 40 км/ч.

ответ:

примерно 2804 см2 или примерно 28 м2

p.s. выглядит правильным

пошаговое объяснение:

у многоклеточных организмов клетки дифференцированы (они отличаютя по строению и выполняют различные функции). это является их явным преимуществом. а что касаемо их недостатков, то на мой взгяд, их нет, они скорее у одноклеточных.

last summer i spent with grandparents. their cottage is close to the small, quiet and beautiful town myshkin on the volga. the house has six bedrooms, three downstairs and three upstairs. grandpa even has his own office, where many, many books and a computer. the most interesting place in the house - the attic. there are many things that are reminiscent of my childhood. the nearest neighbors are very sociable and caring people, they help the grandparents when we do not. as a child i used to spend every summer, poeomu i have a lot of friends. not far from the house - a huge soccer field, and last summer we used to play football. of course we went hiking, paltki broke and slept in sleeping bags. it was great! but not only did i enjoy life, i had to do chores, i vacuumed the entire house. my friends offered to help repair my room. we used a hose from a vacuum cleaner to whiten it. beautiful summer! 2.-anne, i want to talk with you, oh, that again is not it? -look at what a mess kitchen. can not you clean up? , i'm busy, i'm working on the computer. -do not forget, you also have dmashnie duties. i work from morning to night, go shopping, cook dinner. -you're right, mom. after five minutes, i'll wash the dishes clean