Find the ratio of the given one: 20/200 = 0.1
this means the sugar (y) is 0.1 amount of soda (x)
Multiply the amount of soda by 0.1:
Formula is y = 0.1x
So, here we have an exponential function.
Remember that an exponential function has the form:

Where a represents an initial amount, and r is the rate of this amount to change. (Increase, or decrease).
So, given that the population of City A in 2000 was 40 thousand people and the population increased by 13% each year, we can say that

So,

For city B:

But something different happens with city C. This is not an exponential function, this is a linear function.
So,

10x
8x-2
6x+4
They all simplify
1/2x + 3 = 2/3x + 1....multiply everything by the common denominator of 6
3x + 18 = 4x + 6
3x - 4x = 6 - 18
-x = - 12
x = 12 <====
multiplying by the common denominator will get rid of the fractions
The ratio of yellow balloons to blue balloons is 8:12
Then there are 100 balloons. Making the equation, we are able to have:
8X + 12X = 1000
20x = 1000
X = 50.
Yellow balloons = 8x = 8 * 50 = 400 yellow balloons
Blue balloons = 12X = 12 * 50 = 600 blue balloons
So there are 400 yellows balloons.