Paul has 2/3 as many postcards as shawn . the number of postcards shawn has is 3/5 of the number of postcards tim has. if the three boys have 280 postcards altogether, how many more postcards does tim have than paul ?

P = ( 2 / 3 )s;
s = ( 3 / 5 )t ;
p + s + t = 280 ;
Then, p =( 2 / 3 )( 3 / 5 )t ;
p = ( 2 / 5 )t;
We solve the equation : ( 2 / 5 )t + ( 3 / 5 )t + t = 280 ;
( 2 / 5 )t + ( 3 / 5 )t + ( 5 / 5 )t = ( 1400 / 5 )t;
10t = 1400 ;
t = 1400 ÷ 10 ;
t = 140 postcards has Tim;
p = ( 2 / 5 ) × 140 = 56 postcards has Paul;
s = ( 3 / 5 ) × 140 = 84 postcards has Shawn ;