The equation 12 x + 5y=20 represents the total revenue during a one-day fundraiser in the equation x represents the number of youth t-shirts sold and y represents the number of adult t-shirts sold if there were 10 youth shirts sold how many adult t-shirts were sold

If you are solving for the question in the picture your answer would be 18. Whiich is letter A.
 
12x+15y=390         Original Equation
12(10)+15y=390      Replace x with 10
120 + 15y= 390       Mutiply 12 by 10
-120        = -120        subtract 120 on both sides to simplfy the equation
15y= 270                 New equation
÷15 = ÷15                 To get the variable alone divide 15 on both sides
y=18                         Your value for y.

A (18 shirts) is correct.