Question 38561
1. Let x be his speed:
BOb's total time = 7 hours
Mike's total time  = 5 hours
7(60)=5(x)
x=84
Hence, he travelled at 84mph.


2.One jet = x+100
Other jet = x
Equation:
 2.5(x+x+100)=4000
5x=3750
x=
750
750+100=850
Hence, one jet is travelling at 850mph and another one is traveling at 750mph.


3.Letting x be the distance:
Equation:
{{{x/48+x/16=4}}}

{{{48(x/48)+48(x/16)=48(4)}}}
x+3x=192
4x=192
x=48
Hence, the distance is 48miles.


4.Letting x be the distance:
{{{x/300+x/400=7}}}

{{{120000(x/300)+120000(x/400)=120000(7)}}}
400x+300x=840000
x=1200
Hence, the distance is 1200


5.Total time of travel:
4 hours:
Equation:
{{{x/18+x/30=4}}}
{{{540(x/18)+540(x/30)=540(4/1)}}}
30x+18x=2160

x=45
Hence, it can travel 45 miles.
Paul.