Let the number of the shirts of Lexon be A.
She ironed 1/4 or A over the weekend, so 3/4 of A are left to iron during the 5 weekdays.
So Lenox, each week day will iron:

that is 3/20 of A, the total number of his shirts.
If she has 40 shirts, that is if A=40, on Thursday and Friday, she will iron:

shirts.
Answer: 3/20 of the shirts ; 12 shirts