A school snack bar sells a mix of granola and raisins. The mix includes 2 pounds of granola for every 3 pounds of raisins. How many pounds of granola are needed for a mix that includes 24 pounds of raisins?

The easiest way to solve a problem like this is to cross multiply and solve 

The problem gives us a ratio 
2 pounds of granola = 3 pounds of raisins 
which makes a ratio of [tex] \frac{2}{3} [/tex]
The other ratio is 
? pounds of granola = 24 pounds of raisins
which makes a ratio of [tex] \frac{x}{24} [/tex]

To solve, set them equal to each other ...
[tex] \frac{2}{3} = \frac{x}{24} [/tex]

Now we must cross multiply...
To cross multiply, we multiply 2 and 24 
and we multiply 3 and x 
Now we have an equation to solve!
3x = 48 
To solve and get your final answer, divide...
x = [tex] \frac{48}{3} [/tex]

x = 16
You'll need 16 pounds of granola