Question 1007159
{{{(7/10)650+(3/10)720}}} k units of cost.  Just check how the units will work in this expression, and then compute it.


{{{cost=itemCount*price}}}


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Trying again but including shown units:


The ratio shows the ONE part of the 1 kg cut into 7+3=10 parts.  This is  {{{7/10}}} kg of the 650 k/kg tea and  {{{3/10}}} kg of the 720 k/kg tea.  Now account for the requested cost of the two teas.
{{{(7/10)(kg)(650)(k/kg)+(3/10)(kg)(720)(k/kg)}}}----compute this cost.