How to write 6,858.026 in expanded form

This is fractions casey shared a pizza with some friends.they each ate 1 third of the pizza. how many people shared the pizza

The radius of the circle is 4 cm and the measure of the central angle is 90° the area of the sector with a central angle measuring 90° and radius of length 4 cm is vt cm the triangle in the sector is 4 cm the area of the triangle is v/cm² the area of the segment of the circle is (471 - ) cm?

Me. i can't figure out this question. give an explanation too. .