Explanation:
clearly, the price is marked down to $9.60.
so, the 1st and 4th answer options are wrong.
is it marked down by 12% or by 20% ?
the basic price was $12. = 100%
how much are 10% of that ? well, 12/10 = $1.20.
but we marked down by $2.40.
when you compare $1.20 and $2.40, what do to see ?
that the second number is exactly twice the first number.
10%×2 = 20%
therefore, the 3rd answer is correct.