Question 569506
They are approaching each other at the sum of their speeds
Think of one ( either one ) as standing still and the 
other moving at the sum of their speeds
Call the speed of the faster one {{{ 3s }}}
The speed of the slower one is {{{ s }}}
I can say {{{ 48 = ( 3s + s )*2 }}}
{{{ 48 = 6s + 2s }}}
{{{ 8s = 48 }}}
{{{ s = 6 }}}
{{{ 3s = 18 }}}
The speed of the faster cyclist is 18 mi/hr