-20
The factor pairs of -12 are (-12,1)(-6,2)(-4,3)(12,-1)(6,-2)(4,-3)
None of them add up to -8.
77
377
119
61
The factor pairs of 1600 are (1600,1)(800,2)(400,4)(320,5)(200,8)(160,10)(100,16)(80,20)(64,25)(50,32)(40,40) None of them add up to 60. If that was -1600, you could use 80 and -20.
-79
5
20
43
285
77
10
47
112
-151
249
4 x 25