So we want to know which number comes next in the series of numbers 107 98 90 83 77. First we find the pattern: 107-98=9, 98-90=8, 90-83=7, 83-77=6 so now we see that each number in the pattern is smaller by 1 than the previous number. so the next number will be 5 and 77-5=72 and that is the next number. Also the complete number series is: 72-4=68, 68-3=65, 65-2=63, 63-1=62 and finally 62-0= 62.