( 1 + x ) + ( 3 + x ) + ( 5 + x ) + ... + ( 59 + x ) = 2010
( 1 + 3 + 5 + ... + 59 ) + ( x + x + x + ... + x ) = 2010
30x = 2010 - 900
30x = 1110
x = 1110 : 30
x = 37
<=>25x+1+3+5+7+...+59=2010
<=>25x+625 =2010
<=>25x =2010-625
<=>25x =1385
<=>x =1385:25
<=>x =55,4
Vậy x=55,4