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!!
Is there a picture to find the answer?
Answer:
288 Cubic Inches
Step-by-step explanation:
Assuming the cereal takes up 80% of the total volume of the box, you would take 80% of the total volume.
First, do Base x Width x Height for the volume of the box.
10 inches x 3 inches x 1 foot (1 foot is 12 inches)
10 x 3 x 12 = 360
Now, take 80% of 360 cubic inches.
80% is 0.8 times a number
0.8 x 360 = 288
288 Cubic Inches
11 if you multiply 11 by both the number and and the variable you’ll get 11x-55=66. Add 55 to each side which will give you 121 then divide that by 11