The main idea here is to "translate" the words into maths.
First we need to identify the unknowns and label these.
We need to know the number if dimes and the number of quarters. So lets say
x: number of dimes
y: number of quarters
Now lets write equations from the written problem.
We know that there are 36 coind total, thus:
x + y = 36
We also know that the coins total 5.85 dollars, but it is better to count in cents, that is 585 cents.
x are the number of dimes, their value is x*10
y are quarters with value of y*25
thus:
10x+25y=585
We have two equations and two unknowns now, that needs to be solved to get the answer.
x + y = 36
10x+25y=585
C because it is icoceles.
Answer:
One number is 15 and 3 less than that is 12 so that is your other number
So we are given the expression:
÷ 
When we divide fractions, we must flip the second term and change the sign to multiplication:
And then we multiply across:
Then we can break apart all of the like variables for simplification:
When we simplify variables through division, we subtract the exponent of the numerator from the exponent of the denominator. So we then have:
So then we multiply all of these simplified parts together:
So now we know that the simplified form of the initial expression is: 
.
Since it starts at 50 and goes to 35....it is a decrease since the amount is going down, or getting smaller. To find the percent, first find the difference 50-35 = 15; then divide by the initial amount of 50. So, 15/50 = 0.3, and then convert that to a percent by multiplying by 100. Therefore the percent decrease is 30%
