<span>91,910,000 years
</span><span>9.191 x 10^7
answer is c
</span>
The use of grouping symbols in math shows us which part of the problem or expression should be done first. Brackets, braces and parentheses are common grouping symbols used in mathematics. If no symbol is shown between brackets, forexample, (3+7)(8+1) it means that you should multiply after simplifying the operations inside the brackets.
You got both questions correct :)