60*(1-x)=36
60-60x=36
-60x=36-60
-60x=-24
x=24/60
x=4/10
x=2/5
x=0.4
36 is 40% less than 60
A lightning flash has 4 different types of energy
1) Heat energy
2)<span> Light energy
3) Sound energy
4) Electric energy</span>
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 ;
9p + 3p and 2 -2 that is it