3(x + 5) = 39 i dont understand this problem

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

The graph below represents the number of dolphins in a dolphin sanctuary. select all the key features of this function.

If the sales price of a dvd is $20 and the markup is 34%, what is the cost of the dvd?