Answer:
New cost of the sweater is $ 31.5 .
Step-by-step explanation:
As given
A wool sweater originally costs $42.00.
If the sweater is on sale for 25% off .
25% is written in the decimal form

= 0.25
Thus
off on a wool sweater = 0.25 × Originally costs of a wool sweater
= 0.25 × $42
= $ 10.5
Thus
New cost of the sweater = Originally costs of a wool sweater - off on a wool sweater.
Put all the values in the above
New cost of the sweater = $42 - $10.5
= $ 31.5
Therefore new cost of the sweater is $ 31.5 .