Question

abcd+bcd+cd+d=1986 abcd=?

Answer 1

a b c d+
   b c d
      c d
         d
..........................
1 9 8 6

a=1 ; b= 4 ; c= 5 ; d=9
R: 1459+459+59+9=1986

Answer 2

1000a + 100b + 10c +d + 100b + 10c + d + 10c + d +d = 1986
1000a + 200b + 30c + 4d  = 1986
a = 1    200b + 30c + 4d =986 
b = 4      800+ 30c + 4d = 986    30c + 4d = 186    15c + 2d = 93
c = 5      75 + 2d = 93    2d = 18    d = 9
1459