With fractions, you have to make sure their denominator is equivalent/ same. 
For example, if I were to add 1/2 and 3/4, I would need to convert 1/2 into 2/4.
Then I would add then together, and get 5/4, which can be simplified into 1 and 1/4,.
 When adding decimals, you have to line them up. So, lets say I were to add 3.45 and 2.4  
 I would have to line them up like so:
Your answer:5.85.
To add a fraction, you add the numerator(top number) to the other numerator. You also add the denominator(bottom number) to the other denominator. If the denominators are not alike, you have to find the LCD and change the fractions, so that they are alike. For example:
1/2 +3/4
The denominators are unalike. So you have to find the LCD (Least Common Denominator). The LCD is 4. Since 3/4 already has 4 as the denominator, you only have to change 1/2. You change the 2 to 4, so it will look like this: 1/4. You still aren't done. You need to change the numerator. Since you multiply 2 by 2 to get four, you need to multiply 1 by 2. Now you have:
2/4+3/4 You add and get:
Since this is an improper fraction, you have to simplify it. You divide the numerator by the denominator:
5 divided by 4 is 1 with 1 left over. You turn it into a fraction. So your answer is 1 1/4.

For decimals, you align the numbers then add.
1.34 + 56.2

    1.34    See how I aligned the decimal points?
+56.2      That is how you align decimals. Now you just add.
For your answer, the decimal point will be aligned to your 2 other points.