Explanation:
You'll add them it's just like simple addition but you just have to know where the decimal point will be after adding
3.78
+8.94
12.72
When you are adding you start from the back with back I mean the end so when you add 8 plus 4 it's going to be 12 then you write or type the 2 and then carry the 1 and add it to the 7 which is going to be 8 then you add the 8 to the 9 which is going to be 17 that's why we have the 7 there then you carry 1 and add it to the 3 which is going to be 4 and then 4+8 is going to be;12
That's how we got the 12.72
Hope you understand