If the mean of the data 3,21, 25, 17, (x+ 3), 19, (x- 4) is 18, find the value of x. Using this value of x, find the mode of the data.
Find the value of x, if the mode of the given data is 15:
15, 20, 18, 25, 14, 15, 25, 15, 18, 16, 20, 25, 20, x, 18
If both 20 and 18 are changed to 25, find the new mode of the data.