The number is 30 because 30 multiplied by 3 is 90 and 90 -7 is 83
Answer: 
======================================================
Explanation:
Method 1
We can use the pythagorean theorem to find x.

-----------------------------------
Method 2
Use the sine ratio to find x. You'll need a reference sheet or the unit circle, or simply memorize that sin(60) = sqrt(3)/2

-----------------------------------
Method 3
Similar to the previous method, but we'll use tangent this time.
Use a reference sheet, unit circle, or memorize that tan(60) = sqrt(3)

-----------------------------------
Method 4
This is a 30-60-90 triangle. In other words, the angles are 30 degrees, 60 degrees, and 90 degrees.
Because of this special type of triangle, we know that the long leg is exactly sqrt(3) times that of the short leg.

The short leg is always opposite the smallest angle (30 degrees).
Answer:
3375
Step-by-step explanation:
The surface area formula for a cube is:
A = 6 a^2
We know what the area is so plug it into the equation:
1350 = 6 a^2
225 = a^2
a = 15
Now plug a = 15 into the equation for volume of a cube:
V = a^3
V = 15^3
V = 3375
Since all sides are equal, it is an equilateral triangle. Therefore each angle equals 60°.
7x - 3 = 60
7x = 63
x = 9