30,840 is expanses for by place value is 30,000 + 800 + 40. Add them together and you get 30,840.
The equation for this would be 41/4 + 52/3 - 41/3= ?
So then you just change all the denominators to their lcm, which is 12 and multiply the numerator accordingly.
123/12 + 208/12 - 164/12 = 167/12
You would just need to take the square root of 121 since it is square. So:
√121= 11 inches per side
0 if you add the thickness to the underside of the tank
