What is 3 tenths more than 8.154 ? what is 2 and 2 tenths more than 1.425? explain !

8.454 is 3 tenths more than 8.154
3.625 is 2 and 2 tenths more than 1.425

Place values after the decimal point are tenths, hundredths, thousandths, ten thousandths...so on.

So 3 tenths looks like this 0.30 ⇒ 3 is in the tenths place. When you say 3 tenths more, it is a clue that the operation to be done is addition. thus,

   8.154
+ 0.30
  8.454   * in addition or subtraction, the decimal points must be aligned to avoid confusion. 

2 and 2 tenths is like this 2.20 ⇒ 1st 2 is in the ones or units place and the 2nd 2 is in the tenths place. Again it states more than so addition must be done.
 
   1.425
+ 2.20
   3.625