65 + 65 + 65 + 90 + 90 + 90 + 90 + 50 + 50 + 50 + 50 + 50 + 50 + 20 + 20 + 20 + 20 + 20 + 20 + 20 = 995
390
It is 90+90 = 180
90 minus 75 =15 therefore 15 + 75 = 90
42
70
65 + 65 + 65 + 90 + 90 + 90 + 90 + 50 + 50 + 50 + 50 + 50 + 50 + 20 + 20 + 20 + 20 + 20 + 20 + 20 = 995
90 + 65 = 155
-10
90 + 90 + 60 = 240
90
390
It is 90+90 = 180
90 minus 75 =15 therefore 15 + 75 = 90
54 + 560 + 90 = 704
100+80, 99+81, 98+82....
80 + 10 equals 90 so the missing value is zero, ie 80 + 10 = 90 - 0