As you can see, every time x increases by 2, y decreases by 5.
So, we have
N+d=34
.05n+.10d=2.60
Solve by substitution
n=34-d
.05(34-d)+.10d=2.60
1.7-.05d+.10d=2.60
.05d=.90
d=18 dimes
18+n=34
n=16 nickles
Proportional means equal, by the way.
I know that this is a proportional relationship because, if you really look at it, you can see the equality between the three pieces of data. 1/2 = 2/4, and 2/4 mile in 2/3 minute... Divide those two numerators by 2/2 and you get the next data piece. Now, multiply the second data piece by 3/3, and you get the third piece.
Now, look at the numbers I told you to multiply/divide by. They all equal 1. In other words, the only difference between them is the time, the unit rate of the distance (1/4 mile/1/3 min) remains the same.
You add four four times !
428.85 because value= initial value × multiplier^(no of years)
Multiplier=100-0.6
99.4÷100
=0.994
Value= 450 × 0.994^8
=428.847.....
