Question

What is the value of x? A. 3 B. 9 C. 15 D. 30

Answer 1

Answer:

C. 15

Step-by-step explanation:

Assuming that these segments formed from each parallel line are proportional, x/5 = x-6/3.

Now cross multiply by multiplying each denominator by the opposite numerator, this is so the denominators or bottom numbers of each fraction will cancel.

x/5 = x–6/3 → (3)(x/5) = (3)(x–6/3) → 3x/5 = x–6 →

(5)(3x/5) = (5)(x–6) → 3x = 5(x–6) → 3x = 5x – 30.

The last step is to do the basic algebra to find x:

3x = 5x – 30

–5x –5x

[5x will cancel when you subtract both sides by 5x]

-2x = -30

(-1) (-1)

[2 negatives make a positive when -1 is multiplied by an expression with a negative coefficient]

2x = 30

÷2 ÷2

[divide both sides by 2 to simplify 2x to x]

x = 15

_____

You can also check that both sides are proportional because

5 → x

x = 15

5 → 15

3 → x – 6

x = 15

3 → 9

5 × 3 = 15

3 × 3 = 9