Percentages Increase

Please can anyone help me with my following query. I am very confused

Number x has increased by 100% ??
Number x has increased by a factor of 20 ??
Number x has decreased by a factor of 15??
Number x has an increase of 100% ??
Number x has increased to y ??
Number x has increased by y ??

What will be the value of x in each of above 6 cases.