Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

Count the number of balls in picture below:

I am a type of food that is often found in the fridge and can be white in colour. What I am?
Hint 1: I am a dairy product.
Hint 2: You can spread me on the bread.

Can you find the 09 errors in the picture below?

I have Rs.50 and I spend it in the way as below.

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

On a bright sunny day, two fathers took their son fishing in the lake. Each man and son were able to catch one fish. When they returned to their camp, there were only three fishes in the basket. What happened?

PS: None of the fish were eaten, lost, or thrown back.

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?