Answer:
10:6:5
Step-by-step explanation:
a:b=5:3 means a=5*x , b=3*x => a:b= (5*x) : (3*x) (1)
b:c=6:5 means b=6*y, c=5*y (2)
So b=3x=6y => x= 2y => lets rewrite (1) as follows below
a:b= (5*2*y):(3*2*y)=(10*y):(6*y)=10:6 (3)
So from (2) and (3) follows => a:b:c= (10*y): (6*y): (5y)= 10:6:5
