Question 1010364
Standard: S
Extended: E
(you can call them x and y if that's what your teacher wants)
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S= 84
E= 105
84S + 105E= 4998 
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S= 3E In the equation above, let's use this value for E:
84(3E) + 105E= 4998
252E + 105E= 4998
357E= 4998
E= 14 He sold 14 Extended and:
14*3= 42 Standard
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Check:
14*105= 1470
42*84= 3528
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Total...4998 We have the right answer