Answer:
645/28 hours
Step-by-step explanation:
In 1 hour, Kamina does 1/43 of the job.
Simon takes x hour to do the job alone.
In 1 hour, Simon does 1/x of the job.
Together, they do the job is 15 hours, so in 1 hour, they do 1/15 of the job.
1/43 + 1/x = 1/15
15x/(645x) + 645/(645x) = 43x/(645x)
15x + 645 = 43x
28x = 645
x = 645/28