At the city museum, child admission is $5.40 and adult admission is $8.70. On Friday, 170 tickets were sold for a total sales of $1224.90. How many adult tickets were sold that day?

X=number of adult tickets

y=number of children tickets.

we can suggest this system of equations:

x+y=170

8.7x+5.4y=1224.90

We can solve this system of equations by substitution method:

x=170-y

8.7 (170 - y) + 5.4 y=1224.90

1479-8.7y+5.4y=1224.90

-3.3 y=1224.90-1479

-3.3 y=-254.1

y = (-254.1) / (-3.3)

y=77

x=170-y

x=170-77

x=93

Answer:93 adult tickts were sold that day.