Answer: 6 trombones
Step-by-step explanation:
We can set up a proportion.
Let x be the number of trombones there are.
[tex]\frac{4 trombones}{6violas} = \frac{x trombones}{9 violas}[/tex]
We can cross multiply:
4*9 = 6x
6x = 36
Divide both sides by 6:
x = 6