Answer:
Given the statement: A t-shirt shop charges $15 for an adult shirt , $12 for a youth shirt and the total charge for a shirt order was $489.
Let x be the number of adult shirts sold.
and y be the number of youth shirts sold.
as per the given statement;
a shop charges t-shirt for an adult shirt is $ 15
then, total charge of t-shirt for an adult shirt is 15x
Similarly,
a shop charges t-shirt for an youth shirt is $12
then, total charge of t-shirt for an youth shirt is 12y.
Then;
Total charges for a shirt order = total charge for an adult shirt+ total charge for an youth shirt.
⇒ 489 = 15x+12y or
15x+12y =489
Therefore, the equation which can be used to represent x, the number of adult shirts sold and y the number of youth shirts sold is; 15x+12y =489