:lol:
usual 7 seg displays have small LEDs inside, for these LEDs a 15mA current is a little too big, a 5mA current is enough to obtain a good bright, depending of display size.
For unmultiplexed display a single resistor between common anode of every cell in your case of 7447 decoder and +Vcc is a simple case and will work fine if you accept the bright change with number displayed. These common resistors will carry out a current bigger than a single segment current, but be aware if you set up a 7 time bigger current 7*15 in your case, when have 1 on display only 2 segments will share the entire current, so will have 50mA/segment and this is too much. You must make a compromise, and use 7*5mA for example at 35-40mA total current, in this case you have 20mA/segment in max case, and 5mA/segment in min case.
In case of multiplexed display is recommended to use a resistor on every segment(7 resistors in total) and a single decoder. But in this case the segments will bright only a period of time and is off when others cells is on, in this case the medium current through segments of one cell is equal with current through segments when the cell is on, divided at number of cells that are multiplexed. For have a medium current at 5mA for example and if you have 4 cells, you need to calculate your resistors to carry out a 4 time bigger current than medium current, at 4*5mA. But in this case you are help by the fact that the LEDs used in pulsed wave develop a little higher light emission efficiency than the same LEDs used in continuous wave, but this characteristic is deppendent by LEDs type and you can or not to based on it.