This problem can be solved by first assigning the variable x = number of hot water bottles sold. An equation can then be set-up as follows:
312 = 2(10x) + 6(x)
This is the equation because the total sales is $312 while the thermometer and the hot water bottle costs $2 and $6, respectively. Also it should be noted that the number of thermometers sold is 10 times that of hot water bottles sold. After solving the equation, it was determined that 12 hot water bottles were sold.
