Identify and explain the error.

Step-by-step explanation:

Strictly speaking, 15% isn't precisely the same as 0.15; 0.15 is the decimal fraction used to calculate 15% of some quantity.

15% of 52 is indeed 7.8.  $7.80 is the discount that is to be SUBTRACTED  from the regular price ($52).  Adding $7.80 to $52 is incorrect.  

Also, 52 + 7.8 - 59.8 is incorrect:  it's not an equation (but should be one), and we should be subtracting $7.80 from $52.

its 4 because 2 times 2 is 4, if you double the number two you get four

i think the answer is b