x= # of residents
y= # of non residents
QUANITY EQUATION
x+y= 58
COST EQUATION
$13.00x + $17.50y= $925.00
SOLVE FOR 1 VARIABLE
x+y= 58
subtract y from both sides
x= 58-y
SUBSTITUTE IN 2nd EQUATION
$13.00x + $17.50= $925.00
13(58-y) + 17.50y= 925.00
multiply 13 by all in parentheses
(13*58)+(13*-y)+17.50y= 925.00
754-13y+17.50y= 925.00
combine like terms
754+4.50y= 925.00
subtract both sides by 754
4.50y= 171
divide both sides by 4.50
y= 38 number of non residents
SUBSTITUTE TO FIND X
x+y= 58
x+38= 58
x= 20 number of residents
ANSWER: 20 residents and 38 non residents attended.
CHECK:
$13.00(20) + $17.50(38)= $925.00
260 + 665= 925
925 = 925
Hope this helps! :)