Let
x--------> total of images that the memory card can contain
we know that
[tex] \frac{2}{3} x=\frac{1}{4} x+375 [/tex]
Multiply by [tex] 12 [/tex] both sides
[tex] 8x=3x+375*12\\ 8x-3x=4,500\\ 5x=4,500\\ x=900 pictures [/tex]
originally on the memory card
[tex] \frac{1}{4} x\\ =\frac{1}{4} *900\\ =225 pictures [/tex]
therefore
the answer part a) is
[tex] 900 pictures [/tex]
the answer part b) is
[tex] 225 pictures [/tex]