To figure these out, write out the factors of each number you multiply to. Then, go down the list of factors and see which two numbers add to give the 2nd number.
Factors of -80:
-1 80 : 80+ -1 = 79
1 80 : 80 + 1 = 81
2. -40 : -40+2 = -38
-2 40 : 40 + -2 = 38
4 -20 : 4 + -20 = -16
-4 20 : -4 + 20 = 16
5 -16 : 5 + -16 = -11
-5 16 : -5 + 16 = 11
8 -10 : 8 + -10 = -2
8 x -10 = -80 and 8 + -10 = -2 so 8 and 10 is your first answer
Factors of -15:
-1 15 : -1 + 15 = 14
1 -15 : 1 + -15 = -14
1 x -15 = -15 and 1 + -15 = -4 so 1 and -15 is your second answer.
I didn’t write any more factors because I already got the answer.
Try 7 and 8 on your own and let me know if you are stuck/don’t understand anything.
I hope this helps :)