a barista mixes 6 kg of brazilian coffee which sells for 810 per kg wi

Question

A barista mixes 6 kg of Brazilian coffee (which sells for €8.10 per kg) with x kg of Colombian coffee (which sells for €8.60 per kg). He calculates that the fair price for selling the mixture is €8.40 per kg. By modelling this problem mathematically, derive an equation with x's(i)in it. (ii)From the equation in (i), calculate the value for x. A bag contains 6 black marbles and 5 white marbles. A marble is drawn at random from the bag, but not replaced. Another marble is then drawn from the bag.Find the probability that (i)the first marble is black and the second marble is white, (ii)one marble is black and the other marble is white. Thirty students were asked how many minutes they spent on Facebook on a certain day. The grouped frequency distribution table below shows their replies.
(i)Redraw the table, but replace the class intervals with their mid-interval values. Using the mid-interval values, calculate, to the nearest whole number (ii)the mean, (ii)the standard deviation of the data.