Answer:
I believe it would be 250 x .40= 100
Step-by-step explanation:
It would be kind of like if you were shopping and got 40% off a bag.
If the bag was 250 you would pay 150 for it. You would do 250 x .40 (because this a percentage in decimal form) which equals 100. This is what she has read, 150 would be what she has left to read, just like if you were buying a bag, you'd have 150 dollars left to pay....
Hope that makes sense.