Answer:the number of black tiles that Todd used is 27
Step-by-step explanation:
Let x represent the number of black tiles that Todd used.
Todd has 21 white tiles and some black tiles to make a mosaic. Each tile has an area of 3 square. It means that the total area of the white tiles is 21 × 3 = 63 cm^2
The total area of the white tiles is x × 3 = 3x cm^2
The mosaic has a total area of 144 Square centimeters. It means that
3x + 63 = 144
3x = 144 - 63 = 81
x = 81/3 = 27
1. The combined volume of all the tanks at the aquarium is written in Scientific notation. Keeping this on mind, you can write it as following:

2. Now, you must sum the combined volume of all the tanks and the volume of the new tank to calculate the total volume of all of them:
3. Now, you can write the result in Scientific notation, as following:

The answer is: 
Answer:
12862.83cm³
Step-by-step explanation:
Volume of the Box: [L×W×H] or [30x30x30] or [27000cm³]
Volume of the Sphere: [
] (
=pi=3.14) (r=radius=15) or [
×3.14×3375] or [14137.17cm³]
Volume of the empty space: 27000cm³-14137.17cm³=12862.83cm³
Btw there are online tools to help you find the volume of a sphere (just use it after you understand the equation)
Hope I helped!
Answer:

Step-by-step explanation: