Answer: D. 15
Step-by-step explanation:
Given : Brandon mows his lawn once every 5 days.
Thomas mows his lawn every 3 days.
If they are all mowing there lawn today, then the number of days after which they will be mowing there lawn together again= LCM (5, 3)
[LCM= Least common multiple]
Since 5 and 3 are co primes (having no common factor other than 1),
so LCM(5,3)= 5 x 3 = 15
Therefore, they will be mowing there lawn together again after 15 days .
Hence, the correct answer is D. 15 .
