Question 1114162

word problems

At Barney's Takeout Service, the price of an order of french fries is one-half the price of a cheeseburger.  An order of five cheeseburgers and three servings of french fries comes to $10.40 (without tax).  What is the cost of a cheeseburger?
<pre>Let cost of an order of french fries and a burger be F, and B, respectively
Then we get: {{{matrix(1,7, F, "=", (1/2)B, or, F, "=", B/2)}}} ------ eq (i)
Also, 5B + 3F = 10.4 ------ eq (ii)  
{{{matrix(1,3, 5B + 3(B/2), "=", 10.4)}}} ------ Substituting {{{B/2}}} for F in eq (ii)
10B + 3B = 20.8 ------- Multiplying by LCD, 2
13B = 20.8
B, or cost of a cheeseburger = {{{highlight_green(matrix(1,3, 20.8/13, "=", "$1.60"))}}}