What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

Can you make the below equation true by using any three numbers from "1, 3, 5, 7, 9, 11, 13 and 15"?

( ) + ( ) + ( ) = 30

In a mathematical quiz, you are asked the following question:

Use three 9s in a mathematical expression without dividing or multiplying to form the number one.

Can you answer the question?

The dirtier I get, the whiter I look. Who am I?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What is red and smells like blue paint?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it?

There is something which is always coming but never arrives?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.