( 7 + 10 + 13 + …… + 157 ) - (4 + 6 + 8 + …… + 104 )
= (7 + 157)×51/2 -( 4 + 104)×51/2
=82×51 - 54×51
=(82 - 54)×51
= 28×51
= 1428