Adigital camera memory card is 1/4 full. the card is 2/3 full when 375 more pictures have been taken.
a) how many pictures can the memory card hold? ?
b) how many pictures were originally on the memory card? ?

To get the answer first we have to find full numbers.
We can use proportion
2/3 ----------------------- 375
1 -------------------------- x
Crossmultiply now
2/3*x=375           /:2/3 
x= 
x= - its the answer A)
Now we have to find how much were originally on the card.
To get the answer we can just multiply 562 times 1/4.
562*1/4=140 - its the asnwer B)

The clear answer is clearly 25 is very clear to me