Let the number of children tickets sold on Saturday be 10 units

Number of adult tickets sold on Saturday
= 10 units - 120


On Sunday,

The number of child tickets sold increased by 30%. So the number sold is 13 units.

Number of adult tickets sold on Sunday decreased by 10%. 90% of 10 units is 9 units.

10% of 120 = 12
120 - 12 = 108

OR


Number of adult tickets sold on Sunday
is 90% that of Saturday. So 90% of 120 = 108


So number of adult tickets sold on Sunday
= 9 units - 108

Total on Sunday = 816


So 13 units + 9 units - 108 = 816
22 units - 108 = 816
22 units = 816 + 108 = 924
1 unit = 924 ÷ 22 = 42



Therefore,

Number of children tickets sold on Saturday
= 10 x 42
= 420

Number of adult tickets sold on Saturday
= 420 - 120
= 300

Alternatively,

Let the number of adult tickets sold on Saturday be 10 units

Number of children tickets sold on Saturday = 10 units + 120


On Sunday,

The number of adult tickets sold decreased by 10%. So the number sold is 9 units.

Number of children tickets sold on Sunday increased by 30%

30% of 120 = 36
120 + 36 = 156

OR


Number of children tickets sold on Sunday
is 130% that of Saturday. So 130% of 120 = 156


So number of children tickets sold on Sunday
= 13 units + 156


Total on Sunday = 816


13 units + 156 + 9 units = 816
22 units + 156 = 816
22 units = 816 - 156 = 660
1 unit = 660 ÷ 22 = 30



Therefore,

Number of children tickets sold on Saturday
= 30 x 10 + 120
= 420

Number of adult tickets sold on Saturday
= 10 x 30
= 300



You can figure out the $ collected on Saturday on your own from here

Thank you J

You are welcome