Question 1134823
Let {{{ s[1] }}}  = motorist's initial  constant speed in km/hr
In 1/2 hr, he travels {{{ s[1]*(1/2) }}} km
--------------
He needs to make deadline of 2 hrs to get to B
After the 1/2 hr of travel, he loses 18 min, so now
he needs to get to B from location of puncture 
in {{{ 2 - 1/2 - 18/60 }}} hrs
--------------------------------
The distance he has to travel is {{{ 100 - s[1]*(1/2) }}}
I can say:
{{{ 100 - .5s[1] = s[2]*( 1.5 - .3 ) }}}
{{{ 100 - .5s[1] = 1.2s[2] }}}
{{{ s[2] = ( 100 - .5s[1] ) / 1.2 }}}
--------------------------------------
Looking at the total time, I can say:
{{{ 2 = 100/s[1] + 1.2 }}}
{{{ 100/s[1] = .8 }}}
{{{ s[1] = 100/.8 }}}
{{{ s[1] = 125 }}} km/hr
and
{{{ s[2] = ( 100 - .5*125 ) / 1.2 }}}
{{{ s[2] = ( 100 - 62.5 ) / 1.2 }}}
{{{ s[2] = 37.5/1.2 }}}
{{{ s[2] = 31.25 }}} km/hr answer
-------------------------------------
check answer:
{{{ 100 - .5s[1] = 1.2s[2] }}}
{{{ 100 - .5*125 = 1.2*31.25 }}}
{{{ 100 - 62.5 = 37.5 }}}
{{{ 37.5 = 37.5 }}}
----------------------
{{{ s[1]*.5 = 125*.5 }}}
{{{ s[1]*.5 = 62.5 }}} km
and
{{{ s[2]*1.2 = 31.25*1.2 }}}
{{{ s[2]*1.2 = 37.5 }}}
{{{ 62.5 + 37.5 = 100 }}}
OK
----------------------------
That's as far as I can go due to time