Question 1176261
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Since they want a system of linear equations, we will use two variables.<br>
x = number of sandwiches
y = number of drinks<br>
7x = cost of the sandwiches at $7 each
2y = cost of the drinks at $2 each<br>
The total number of items is 10:
{{{x+y = 10}}}<br>
The total cost is $40:
{{{7x+2y = 40}}}<br>
Double the first equation and compare it to the second:<br>
{{{7x+2y = 40}}}
{{{2x+2y = 20}}}<br>
The difference is<br>
{{{5x = 20}}}
{{{x = 4}}}<br>
The number of sandwiches ordered was x=4.<br>
Informally, that means the number of drinks was 10-4 = 6.<br>
Formally....<br>
{{{4+y = 10}}}
{{{y = 10-4 = 6}}}<br>