Answer:
Calculate the average of the five original cards:
2+5+7+8+9=31
31/5 = 6.2
So, if a card was removed, the four remaining cards would have an average of 6, meaning that they would add up to 24.
31-x=24?
Subtract 31 from both sides: -x=-7
Divide by -1 on both sides: x=7
So, we know that 7 was removed.
Let me know if this helps!
