Question 633332
I like to solve these by thinking of one plane as stationary
( maybe sitting on the runway ) and the other one 
flying at the sum of their speeds.
Let the speed of the slower plane = {{{ s }}}
The moving plane will cover {{{ 2025 }}} mi in {{{ 3 }}} hrs
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{{{ 2025 = ( s + s + 35 )*3 }}}
{{{ 2025 = 6s + 105 }}}
{{{ 6s = 2025 - 105 }}}
{{{ 6s = 1920 }}}
{{{ s = 320 }}}
{{{ s + 35 = 355 }}}
The faster plane's speed is 355 mi/hr
The slower plane's speed is 320 mi/hr
check:
{{{ 2025 = ( s + s + 35 )*3 }}}
{{{ 2025 = ( 320 + 355 )*3 }}} 
{{{ 2025 = 675*3 }}}
{{{ 2025 = 2025 }}}
OK