Question 1174290
x and 290-x is the one variable method
5x+7(290-x)=1790
-2x+2030=1790
-2x=-240
x=120 at $5 ($600) advance
290-x=170 at $7 ($1190) at the door
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x+y=290
5x+7y=1790
-5x-5y=-1450
2x=340
x=170 at the door or $1190 at the door
y=120 in advance or $600 advance