Let the number be a ....
=>Number doubled : 2a ..
=>Eight less than the no. Doubled : 2a - 8
=>Eight less than the no. doubled is 20 more than the no. : 2a - 8 = 20 + a
=>2a - 8 - 20 - a = 0
=>2a -a - 20 -8 = 0
=>a -28 = 0
=>a = 28
=>so the number is 28...
Hope it helps!!!
