6×2900÷3 what is that squared and why will it be that number

I'm assuming you mean the whole expression is squared?

Remember your order of operations.
PEMDAS- parentheses, exponents, multiplication, division, addition, subtraction. Work inside the parentheses first. Within the parentheses, multiply before dividing.

=(6×2900÷3)^2
multiply first within parentheses

=(17,400÷3)^2
divide next

=(5,800)^2
square (or multiply 5800 by itself)

=5800 * 5800

=33,640,000

ANSWER: 33,640,000 is the answer because according to the order of operations (PEMDAS), we work inside the parentheses first. Within the parentheses we multiply first and then divide. Finally we square that answer.

Hope this helps! :)