Answer: See below
Explanation:
3x - 4y = 13 (1)
2x + y = 5 (2)
——————
3x - 4y = 13
4(2x + y = 5) (2) times 4
——————-
3x - 4y = 13
8x + 4y = 20
——————-
11x = 33
x = 33/11
x = 3
Plug x = 3 in (2):
2(3) + y = 5
6 + y = 5
y = 5-6
y = -1
Thus, x = 3 and y = -1

If 2x+y=5, then y=5-2x, so he substituted 5-2x correctly.
x+4x=5x, so he combined like terms correctly.
If 5x-10=10, then 5x=10+10 -> 5x=20, so he subtracted 10 from the right side instead of adding 10 to the right side.
The answer is C.
Here's the correct solution:
Answer:
x = 8
Step-by-step explanation:
Given 2 intersecting chords in a circle, then the product of the parts of one chord is equal to the product of the parts of the other chord, that is
5x = 4 × 10 = 40 ( divide both sides by 5 )
x = 8