Let the number of pictures the card holds = X
The card is already full by 1/4 = X/4
when 375 more pictures are taken then card is full by 2/3
Then
X/4+375= 2X/3
(2X/3)-(X/4)=375
(8X/12)-(3X/12)=375
5X/12=375
X=(375*12)/5
X= 900
So the total number of pictures memory card can hold = 900
Number of pictures originally on the memory card = X/4
= 900/4
= 225