Answer:
$42 would be the cost of the shirt after the discount. The difference between the price of the shirt before the discount, and after is $18.
Explanation:
If you divide 60 by 100, you would get the value for 1% of $60. If you multiply that number by the discount amount, you get the amount that is going to be subtracted from the cost when the discount is applied.
60 / 100 = 0.6
0.6 x 30 = 18 (This is the difference)
60 - 18 = 42 (This is the value after the discount)
Thus the value after the discount is $42, and he difference between the 2 values is $18.