Question 1149813
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<pre>
Let M be the number of the mid-size cars and

let F be the number of the full size cars.


Then you have these 2 equations in 2 unknowns

       M +     F =   60       (1)    (counting cars)

     13*M + 18*F = 1000       (2)    (counting money in thousand dollars)


Using substitution method, from equation (1) express  M = 60 - F  and substitute it into equation (2). You will get


     13*(60-F) + 18F = 1000.   (3)


Simplify; express F and calculate

     F = {{{(1000- 13*60)/(18-13)}}} = 44.


<U>ANSWER</U>.  44 full size cars,  and the rest,  60-44 = 16 mid-size cars.


<U>CHECK</U>.   44*18 + 16*13 = 1000 thousands dollars.  ! Precisely correct !
</pre>

Solved.


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Buying tickets; buying shirts and socks; buying roses and violets; counting calories and grams of fats in combined food;

buying oranges and apples --- all these problems are of the same type and can be solved by the same method.


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