Jill had $90. she bought a skirt that normally costs $42 but was on sale for half price. she also bought a t-shirt that was $8 off its regular price. before sales tax, the total cost of the clothes was $31. what was the regular price of the t-shirt?

As the skirt is on half price, this means that $42/2= $21.
Therefore, the cost of the skirt is $21.
If the total cost for the two items is $31, you need to subtract $21 from $31, and this gives you $10. 
If the T-shirt has $8 off, $10+$8= $18
Therefore, the original price of the T-shirt is $18
Hope this helps :) 

There would be 36.35 pounds