On question three . also give explanation you so much.

Let the number be x.

double it and add 5
⇒ 2x + 5

The result is 1 less than the number she thought of
⇒ x - 1

Construct the equation to solve for x:
2x + 5 = x - 1 
x + 5 = -1           // Take away x from both sides
x = -6                // Take away 6 from both sides


Answer : The number Tui first thought of is -6.

The answer would be 54.2%.