Question 636592
let’s {{{x}}} be the speed of one plane in miles per hour, and
{{{y }}} the speed of the other in miles per hour

given:

{{{x = y + 100}}}

{{{x / 2000 = y / 1500}}}.....substitute {{{x}}}

{{{(y + 100) / 2000 = y / 1500}}}....solve for {{{y}}}

{{{y / 2000 + 1 / 20 - y / 1500 = 0}}}

{{{-0.000167*y = -0.05}}}

{{{y = (-0.05)/-0.000167}}}

{{{y = 300 mph}}} 

{{{x = 300 + 100 = 400 mph }}}