A boat travels 8 km upstream and 8 km back. The time for the round trip is 2 hrs. The speed of the stream is 4 km/hr. What is the speed of the boat in still water?

According to modern science, earth is about 4.5 billion years old and written human history extends back about 10,000 years. suppose the entire history of earth is represented with a 10-meter-long timeline, with the birth of earth on one end and today at the other end.

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers