Given :
Ronald and Tim both did their laundry today, June 1st.
Ronald does his laundry every 6 days
Tim does his laundry every 9 days
The number of days of June = 30 days
so, the days that Ronald did his laundry are : 1 , 7 , 13 , 19 , 25 , 30
And the days that time did his laundry are : 1 , 10 , 19 , 28
so, the number of days they do their laundry on the same day = 2
Another solution:
The multiple of 6 are : 6 , 12 , 18 , 24 , 30
the multiple of 9 are : 9 , 18 , 27
The common multiple = 18
so, the answer is they do their laundry at 1 , 19
So, the answer is 2 days