There are two triangles here: ABC and ADF. These triangles are similar, and thus proportional. So, we can set up a proportion between the left side of each triangle and the base of each triangle.
AB / AD = BC / DE
4 / (4 + BD) = 5 / 9
---AD is made up of AB and DB. We know AB, but not BD, so we need to find its value to find the length of AD.
5(4 + BD) = 9 x 4
20 + 5BD = 36
5BD = 16
BD = 3.2
AD = AB + BD
AD = 4 + 3.2
AD = 7.2
Hope this helps!

- A common unit of measurement for water's density is gram per milliliter (1 g/ml) or 1 gram per cubic centimeter (1 g/cm3). Actually, the exact density of water is not really 1 g/ml, but rather a bit less (very, very little less), at 0.9998395 g/ml at 4.0° Celsius (39.2° Fahrenheit).
- Water density changes with temperature and salinity. Density is measured as mass (g) per unit of volume (cm³). Water is densest at 3.98°C and is least dense at 0°C (freezing point). Water density changes with temperature and salinity.
- When water is a liquid, the water molecules are packed relatively close together but can slide past each other and move around freely (as stated earlier, that makes it a liquid). Pure water has a density of 1.000 g/cm3 at 4˚ C. As the temperature increases or decreases from 4˚ C, the density of water decreases.
Step-by-step explanation:

If B is the midpoint of AC, that means that the distances from A to B and B to C are the same. The distance from A to B is 8x + 4, and the distance from B to C is 10x - 6, so we can set these two equivalent:
8x + 4 = 10x - 6
Solving for x:
4 = 2x - 6 (subtract 8x from both sides)
10 = 2x (add 6 to both sides)
5 = x (divide both sides by 2)
So, x = 5, which is the second option given.
Substitute the 7 in anywhere there is an x.
49-5=44