At the city museum, child admission is $6.10 and adult admission is $9.90. On Friday, 142 tickets were sold for a total sales of $1185.40. How many child tickets were sold that day?

no of child tickets sold were 58

Step-by-step explanation:

Let the number of child ticket sold be x

cost of 1 child ticket = $6.10

Total cost of x child ticket = x*cost of 1 child ticket = = $6.10x

Let the number of adult ticket sold be y

cost of 1 adult ticket = $9.90

Total cost of y adult ticket = y*cost of 1 adult ticket = = $9.90y

Given total ticket sold = 142

Thus,

number of child ticket sold +  number of adult ticket sold = 142

x + y = 142   - equation 1

x = 142 -y  

Total sales of ticket = $1185.40

total sales of ticket  = Total cost of x child ticket + Total cost of x a dult ticket

6.10x + 9.90y = 1185.40

in this equation substituting x = 142 - y from equation 1

6.10(142 - y )  + 9.90y = 1185.40

=>866.2 - 6.10y + 9.90y = 1185.40

=> 3.80y = 1185.40 - 866.2

=> 3.80y = 319.2

=> y = 319.2/3.80 = 84

Thus, y = 84

x = 142 - y  = 142 - 84 = 58

Thus, no of child tickets sold were 58