The numbers are: 20 and -48
The middle number for 150 and 280 is 215. Here's how you work it out: Add the two numbers together which makes a total of 430. Then you divide the number by the number of numbers you added together to give you your answer.
The two numbers you multiply together to equal 391 are 17 by 23.
The two numbers are -2 and -15
The two numbers are... -36 and -36
280
-313
45
1 x 280, 2 x 140, 4 x 70, 5 x 56, 7 x 40, 8 x 35, 10 x 28, 14 x 20
12x12
The numbers are: 20 and -48
-144
736
-82
69
-17
11 and 11