Your first example is "fourteen plus four divided by two".
Both of your other examples are "fourteen times four plus two". Obviously this means there is an ambiguity in the spoken form. You could read the first one as "multiply fourteen by four and then add two" or the second one as "fourteen times the sum of four and two" if you want to make them unambiguous. But usually it's easier to just write them in mathematical notation instead.
In addition to the very correct info provided by The Photon, another possibility to reduce ambiguity in spoken English (and one I personally like to use) is to use the phrase "the quantity" for parts in parentheses. If necessary, you'd combine this with brief pauses when speaking to make clear where the parens stop.
Using this logic:
- the quantity fourteen plus four brief pause divided by two
- fourteen times four plus two
- fourteen times the quantity four plus two
We use mathematical notation because expressing this in spoken Language is difficult.
So how would you do it in your language?
There are multiple strategies. If you want to exactly capture the mathematical expression with no ambiguity:
Open bracket, fourteen plus four, close bracket divided by two
You can make that shorter, but less clear using intonation and pausing
fourteen plus four(rising intonation) (pause) divided by two(falling intonation)
Or you can paraphrase
Add together fourteen and four and divide the answer by two.
Half of the sum of fourteen and four
You can paraphrase mathematically
Half of fourteen plus half of four.
However, are you planning on being a maths teacher in the future? If so "Good Luck! (we need more maths teachers). If not, you won't ever need to use this. Arithmetic is a written language, not a spoken one.