(1) The value of a two-digit number is 3 times the sum of the two digits.If 9 is added to this two-digit number, the new value will be 4 times the sum of the two digits. Find the two-digit number.
(2) A boat takes 3 hours to reach a destination 48 km apart when it goes downstream and takes 4 hours for the return journey. What is the speed of the boat? What is the speed of the water current?
(3) Beer A contains 8% of alcohol by volume and beer B contains 3% of alcohol by volume. The brewer mixes beer A and beer B to produce a new beer that contains 5% of alcohol by volume. How much beer A and beer B should he mix to produce 1000mL of new beer respectively?