Step-by-step explanation:
Logan can complete 1/5 of the job each hour, and Angis can complete 1/7 of the job each hour. Thus, together, they complete 12/35 of the job per hour: (1/5 + 1/7 = 7/35 + 5/35 = 12/35).
In one hour they complete 12/35 of the job, so:
1 hour * 35 = 12/35 jobs
35 hours = 12 jobs
35 hours / 12 = 1 job
2.916 hours = 1 job
.916 hours = 54.96 minutes
.96 minutes = 57.6 seconds ≈ 58 seconds
Hope it helps :) and let me know if you want me to elaborate.