Question 939015
There are two variables 
price  for adult and cost for child

Let price for adult be x
and price for child be y

Group I
10 adults and 8 children
they paid $136
write the equation
10x+8y=136...................(1)

Group II
17x+2y=150...................(2)

solve the two equations by elimination method
multiply equation (2) by -4
we get 
-68x-8y=-600...................(3)

add equation (1) & (3)

we get
-58x=-464

/-58
x= -464/-58

x= 8
$ 8 for adult

Plug x in the equation (1)

10x+8y=136
10*8 + 8y=136
80+8y=136
8y=136-80
8y=56
/8
y = 7 
$7 price for child