Mr. Johnson purchased 20 concert tickets for a total of $225. The concert tickets cost $15 for adults and $10 for children under 12. How many tickets for children under 12 did Mr. Johnson purchase?

15

Step-by-step explanation:

Let the number of adult tickets be x while children ticket be y. Since the total tickets were 20 then we can form the equation

x+y=20

Making x the subject then x=20-y

Considering the cost of each ticket

15x+10y=225

Substituting x with 20-y then

15 (20-y) + 10y=225

300-15y+10y=225

Collecting like terms

300-225=15y-10y

75=5y

Y=75/5=15

To find x, we already know that x=20-y hence x=20-15=5

Therefore, children tickets are 15 while adult tickets are 5.

The question only needs us to know the children tickets, y which is 15