Can anyone give me the answer to this i’ve been stuck on this question for a week now

Trevor and marissa together have 26 t-shirts to sell. if marissa has 6 fewer tshirts that trevor, find hiw many tshirts trevor has. identify the if-than moves in your solution

How many different three-digit numbers can be formed using the digits 1 comma 2 comma 9 comma 6 comma 4 comma 3 comma and 8 without repetition? for example, 664 is not allowed.

6x + 3y = -6 2x + y = -2 a. x = 0, y = -2 b. infinite solutions c. x = -1, y = 0 d. no solution