Solution:

The hidden cat is encircled below.

Solution:

39.

Solution:

D & C.

For details, Please check the video.

Solution:

It can be done as shown in the video below.

Solution:

75.

For a detailed explanation, please watch the video.

Solution:

16

Watch Video for more explanation.

Solution:

30.

For Explanation, watch video

Solution:

It can be done as shown in the picture below. You can also watch video For more explanation.

Solution:

Chilli no. 4.

Watch the video for an explanation.

Solution:

15

Explanation:
3drink = 30 ....... EquationA
1drink + 2 burger = 20 ....... EquationB
burger + 4 fries = 9 ....... EquationC
burger + fries * drink = ?

From EquationA
drink = 10

From EquationB
burger = (20-10)/2 = 5

From EquationC
fries = (9-5)/4 = 1

Hence
burger + fries * drink = 5 + 1 * 10 = 5 + 10 = 15