Question 622171
first make the statement: x+y+z=144
since the second is twice as long as the first, this means, 
y=2x
now the third is 20 inches longer than the first, so we have:
z=20+x

so we get x+(2x)+(20+x)=144

4x + 20 = 144
4x=124
x= 31

now by the statements y=2x and z=20+x we see that y>z>x so y is the longest piece of pipe at 62 inches long, so to find the cost we get,

62*0.08 = $4.96