20,13 x 90 + 20 +10,065 x18 + 0,13
= 20,13 x90 + (20 + 0,13 ) + 10,065 x18
= 20,13 x90 + 20,13 x1 + 10,065 x18
= 20,13 x( 90 +1 ) + 10,065 x18
= 20,13x91 + 10, 065 x18
= 20,13 x 91+ (10,065 x2) x9
=20,13 x91 + 20,13 x9
= 20,13 x( 91 + 9)
= 20,13 x 100 = 2013 .