In what situation do we need to use substitution rule? what is the purpose for using substitution rule?

Substitution rule is one of the most important rule to solve the integrals problem.

In substitution rule we substitute  different  variable in such a way that it can simplify the question.

example: when we have to solve "Sin x²" we cannot solve it but

               if question is "x  Sin x²" we can substitute x² with t and can solve it.

The purpose of substitution rule is to simplify the problem of integrals.

13.33%

say 50 oranges, then 100 apples

80 are red, 20 are yellow

total fruit = 150

20chances out of 150 for yellow

20/150 = 13.33%