Answer:
The number of adult's for the dinner is 4 and
The number of child's for the dinner is 6 .
Explanation:
Given as :
The total number of members goes for dinner = 10
The total bill for the dinner = $ 66
Let The number of children goes for dinner = C
And the number of adults goes for the dinner = A
The charges for the adults dinner = $ 9 per plate
The charges for the child dinner = $ 5 per plate
So, According to question
A + C = 10 ......1
9 A + 5 C = 66 ....2
Solving eq 1 and 2
So, 9 × ( A + C ) = 9 × 10
Or, 9 A + 9 C = 90
9 A + 5 C = 66
or, ( 9 A + 9 C ) - ( 9 A + 5 C ) = 90 - 66
Or, ( 9 A - 9 A ) + ( 9 C - 5 C ) = 24
or , 0 + 4 C = 24
∴ C =

I.e C = 6
Put The value of C in eq 2
so, 9 A + 5 C = 66
or, 9 A + 5 × 6 = 66
or, 9 A + 30 = 66
Or, 9 A = 66 - 30
Or, 9 A = 36
∴ A =

i.e A = 4
Hence The number of adult's for the dinner is 4 and The number of child's for the dinner is 6 . answer