First, calculate what is 40% of the regular price equal to and substract it from the regular price to find the sales price of the sweaters.
Since the regular price is $37, then:
The total discount on the purchase of two sweaters is 14.8*2=29.6, which is equal to 29.6/4 = 7.4 off each sweater, which is 20% off each.
Then, if Joanie buys two sweaters at the regular price and two on sale, she will save 20% off the total cost. Then, Joanie is incorrect.