The sum of your two factors must be -5. Which of your factor pairs above could produce this sum? A: 6and 6
B 5 and 1
C 36 and 1
D 4 and 8
E 2 and 18
F 3 and 12
G 1 and 1
H 4 and 9

x=number of shirts
y=number of DVDs
We can suggest the following system of inequalities.
30x+12y<175

We solve for x:
maxmimun number of y: y<175/12; y<14
30x+12y<175
30x<175-12y
x<(175-12 y)/30           " y" can be:0,1,2,,14

Answer 1= the solution for shirts would be x<(175-12y)/30   ;  
"y " can be:0,1,2,...,14

We solve for y;
 maximum number of DVDs:    x<175/30<5

30x+12y<175
12y<175-30x
y<(175-30x)/12;        "x" can be: 0,1,2,3,4,5.

answer 2: the solutions for DVDs would be: y<(175-30x)/12; 
"x" can be: 0,1,2,3,4,5.