= 3 * (5 – 6) + 2 * 54 – 5
= -3 + 108 – 5
= 105 – 5
= 100

30.

There are:

16 1×1 squares
9 2×2 squares
4 3×3 squares
1 4×4 square (the whole shape)

Hence, 16 + 9 + 4 + 1 = 30.

It has a hole. The hole is the thing (although it could be argued a pocket has air, darkness or dust and so on).

Because the numbers on a phone would spell the word RIDDLES.

Edam cheese.

Look at it upside down. Instead of changing the equation, you can change your perspective.

This is from Dan Brown’s novel, Origin.