It's the first one, an algebraic expression contains variables
First of all, the modular inverse of n modulo k can only exist if GCD(n, k) = 1.
We have
130 = 2 • 5 • 13
231 = 3 • 7 • 11
so n must be free of 2, 3, 5, 7, 11, and 13, which are the first six primes. It follows that n = 17 must the least integer that satisfies the conditions.
To verify the claim, we try to solve the system of congruences

Use the Euclidean algorithm to express 1 as a linear combination of 130 and 17:
130 = 7 • 17 + 11
17 = 1 • 11 + 6
11 = 1 • 6 + 5
6 = 1 • 5 + 1
⇒ 1 = 23 • 17 - 3 • 130
Then
23 • 17 - 3 • 130 ≡ 23 • 17 ≡ 1 (mod 130)
so that x = 23.
Repeat for 231 and 17:
231 = 13 • 17 + 10
17 = 1 • 10 + 7
10 = 1 • 7 + 3
7 = 2 • 3 + 1
⇒ 1 = 68 • 17 - 5 • 231
Then
68 • 17 - 5 • 231 ≡ = 68 • 17 ≡ 1 (mod 231)
so that y = 68.
Answer: x = -3, y = 2, z = 4
Step-by-step explanation:
Answer:

Step-by-step explanation:
Since ED is parallel to CA, the two triangles in the figure share all 3 angles and therefore must be similar. By definition, the corresponding sides of similar polygons are in a constant proportion.
Therefore, we have:

Answer:
305.78 in2
Step-by-step explanation:
The rocket has two parts: one is a cylinder and the other is a cone.
To find the total volume of the rocket, we need to find firstly the volume of each part.
The cylinder has a radius of 2 inches and a height of 2*12 + 5 - 7 = 22 inches, so its volume is:
V1 = pi * r^2 * h = pi * 2^2 * 22 = 276.46 in2
The cone has a radius of 2 inches and a height of 7 inches, so its volume is:
V2 = (1/3) * pi * r^2 * h = (1/3) * pi * 2^2 * 7 = 29.32 in2
Then, we have that the volume of the rocket is:
V = V1 + V2 = 276.46 + 29.32 = 305.78 in2