Answer:
412 adults
Step-by-step explanation:
Let the number of adults be x
Let the number of children be y
If a total of 1,236 people attended the concert, then;
x + y = 1236 .....1
If there were twice as many adults as children who attended the concert, then;
y = 2x
Substitute y = 2x into 1
x + 2x = 1236
3x= 1236
x = 1236/3
x = 412
Hence 412 adults attended the concert.