Yes.
21
20 = 400
12 + 16 + 18 + 20 + 9 = 75
If: m = 20 Then: 3m+18 = 78
If: x+18 = 20 Then: x = 2
18 + 10 + 20 + 30 + 15 + 50= 143
16
If a, b, c, and d are positive integers that add up to 20 they each must be less than 20. If abcd=81 then a, b, c, and d must be factors of 81. The factors of 81 are 1,3,9 then 27, so there is no solution to this problem.
Negative 2 - negative is 18 integers. Positive 18 to negative is 20 integers.
20+3b = 20 + 3(-6) = 20-18 = 2
2 times -20 equals 40 and 2 plus -20 equals -18
The integers are 18 and 20.