40x40x40+26-98+45x78x78x78 then divide by 3

You've written "then" before 3, so i assume the real question is:

(40 * 40 * 40 + 26 - 98 + 45 * 78 * 78 * 78) / 3
Use "PEMDAS" first solve under the parenthesis, then after it.

= (64000 + 26 - 98 + 21354840) / 3
= 21418768 / 3
= 7139589.33

In short, Your Answer would be: 7139589.33

Hope this helps!

The answer is the third choice