Question 977948
3t=2*r
r=a+b+c
2*(a+b+c)=3t
coins
1,5,10,25,50,100
if Tom has three alike he has 
3,15,30,75,150 or 300
so Rebecca has a total of 1.5, 7.5, 15, 27.5, 75 or 150
she can't have 1.5, 7.5, 27.5
so she must have 
15, 75 or 150
she needs three different coins to add up to 15, 75 or 150 
5 and 10 add up to 15 but are only two coins

same with 75 cents 25 and 50 add up to 75 
and also with 150 
there are no current  coins in circulation that meet the requirements