A machine consists of two components, whose lifetimes have the joint density function 1 , 0, 0, 10 (, ) 50 0, otherwise. x y xy f xy   > > +< =    The machine operates until both components fail. Calculate the expected operational time of the machine.

If f(x) = 4 - x2 and g(x) = 6x, which expression is equivalent to (g-f)(3)? 06-3-(4 + 3)2 06-3-(4-33 6(3) - 4 +32 6(3) -4 -32

In a newspaper, it was reported that yearly robberies in springfield were up 25% to 265 in 2013 from 2012. how many robberies were there in springfield in 2012?

Talia took the bus from her home to the bank and then walked back to her home along the same route. the bus traveled at an average speed of 40 km/h and she walked at an average speed of 5 km/h. to determine the time, x, that it took talia to walk home, she used the equation 40(0.9 – x) = 5x. the time of trip 2 is hours. the distance of trip 1 is km.