Tyler can shovel the driveway in 2 hours dakota can complete the job in 90 minutes if they work together how long will it take

One JOB = 1  and 2 hours = 120 min

Tyler Rate per minute: 1/120 (in 1 minute he performes 1/120 of the job)
Dakota Rate per minute: 1/90 (in 1 minute he performes 1/90 of the job)

Tyler's + Dakota's rate per 1 minute = 1/120 + 1/90  = 7/360 (Job/minutes)

7/360 of the job was performed in 1 minute
a complete JOB =1 to be performed in x minutes (Rule of three)

x = 1x1/(7/360) that equals to 360/7 and x (time of both) = 51 min 42

Ithink it's the first one ( let me know if it right)