Question 780830
Linear system of equations.

Let x = count of burgers
Let y = count of chocolate bars
Given information makes {{{x=3y}}}
cost for the burgers, {{{x*30}}}
cost for the chocolate bars, {{{y*55}}}


Actual cost spent was 700 Php, so this must be the sum of the costs of each product.
{{{highlight(30x+55y=700)}}}
and 
{{{highlight(x=3y)}}}, as found earlier.


Easiest way to handle the system is use the formula for x to substitute into the total cost 700 equation, and solve for the y value.  Return again to the formula for x and use the y value to compute x.


-----------Skipping the steps from there, and keeping results as rational numbers,-------------
{{{x = 420/29}}}
{{{y = 140/29}}}