The mathematical word describing both and
in the expression
is "<u><em>addition</em></u>"
You can represent the unknown amounts by the use of variables. Follow whatever the description is and convert it one by one mathematically. For example if it is asked to increase some item by 4 , then you can add 4 in that item to increase it by 4. If something is for example, doubled, then you can multiply that thing by 2 and so on methods can be used to convert description to mathematical expressions.
For the given case, the terms were and
and the expression formed from them is
This means both the terms were added together, as denoted by '+' (called 'plus') sign.
When two terms are written with 'plus' sign in between, then that means they're added to each other and the result will be addition of both of their's values.
Thus, the mathematical word describing both and
in the expression
is <u><em>addition</em></u>"
Learn more about addition here: