Hi Nivetha,
This is Ex 12.2, 3 of Class 10, please check it here https://www.teachoo.com/1865/548/Ex-12.3--2---Find-area--if-radii-of-two-concentric-circles/category/Ex-12.3/
To learn all questions of Chapter 12 Areas related to Circles, please visit https://www.teachoo.com/subjects/cbse-maths/class-10th/ch12-10th-areas-related-to-circles/serial-order-wise/