What is the value of x in the proportion start fraction x plus 1 over x plus 3 end fraction equals start fraction 15 over 21 end fraction?

Question

(1 point)
Responses

4
4

start fraction 1 over 3 end fraction
Image with alt text: start fraction 1 over 3 end fraction

one-fourth
Image with alt text: one-fourth

3
3

Answer 1

The correct answer is 3.
x + 1 over x + 3 = 15 over 21
Cross multiply to get (x + 1) * 21 = 15 * (x + 3)
21x + 21 = 15x + 45
6x = 24
x = 4

Therefore, the value of x is 4, which is not listed as an option. Please check the calculations to verify the correct answer.