Question 1164534
small flat rate  php 5,   x of these
medium flat rate php 10.5,  y of these

cost,  php 110
boxes, 12


{{{system(x+y=12,5x+10.5y=110)}}}



{{{x+2.1y=22}}}
{{{and}}}
{{{x+y=12}}}


Equating the x expressions,
{{{22-2.1y=12-y}}}
{{{22-12=2.1y-y}}}
{{{10=1.1y}}}
{{{y=9.0909}}}....
{{{}}}
Notice the question,  "The total cost was <b>about</b> Php 110."  This means taking the most reasonable whole number result is necessary.
Best choice here is {{{highlight(y=9)}}}, and then {{{highlight(x=3)}}}.


The actual cost for the total packages must be  {{{5*3+9*10.5=109.5}}}
or {{{highlight(109.5Php)}}}.