What does braces means in math terms?

What is the number eight millionthree hundred thousand fifty three and four hundredths in standard form? What is 4.2 x 10 to the power of -4? 100000000 plus 20000000 plus 5000000 plus 600000 plus 90000 plus 600 plus 4 plus 0.1 plus 0.09 in standard form? What is 386 km in miles? What is the mean of 70 70 72 68 68 66? How come 2x2 equals 4 and 3x3 equals 9 not 6? What is 0.000000067 in scientific notation? What is 3.052 times 103 in standard notation? How many dimes are in 15 quarters? How many number of digits are there in a Swiss bank account number? What is 7 subtracted from what equals -15? 123 is the answer what is the question? 2 over 3 divided by 5? What is 53 divided by 6324? What is the most used word in the Bible and how many times used? What number should be added to 8 to get a sum of -8? What is 5 cm squared? What is 789.96 rounded to the nearest tenth? Compare and contrast the metric and English systems of measurement? What is 40 60?