Jai the fastest encoder can finish a job in 30 minutes. Ana who can finish the same job in 1 hour and Kim whi can do the same in 40 minutes,

"Let x = minutes

Jai can do 30/30 minutes in one job

then, Jai can do 1/30 per minute

Ana can do 60/60 minutes in one job

then, Ana can do 1/60 per minute

Kim can do 40/40 minutes in one job

then, Kim can do 1/40 per minute

Math Equation:

(1/30x + 1/40x) + 1/60x = 1

Solve for x:

(1/30x + 1/40x) + 1/60x = 1

LCD = 120

(3x + 4x) + x = 120

7x + x = 120

8x = 120

x = 15

Answer: 15 Minutes"