29 students have to be in the class. If 29 students each pay 2.75, they will raise up 79.75 dollars! :)
If you have 8 yellow balloons for every 12 blue balloons, then if you have 20 balloons in total, 8 out of 20 of those balloons will be yellow. Then you can set up this ratio:

Then, you can use either cross multiplication or multiply the numerator and denominator by the same number to help solve for x. Personally, I prefer cross multiplication, so that's what I'll show you here:

Finally, solve for x:

If you had 100 balloons, you will have
40 yellow balloons.
Hope this helps!!
The best choice is 'C'. If it's 1, 5, and 4, then ideally, in 100 draws, you would expect 10, 50, and 40 ... pretty close to Tyrell's actual experimental results.
I’m having a hard time understanding your question