Answer:
x=5
Step-by-step explanation:
f(x) = 7
We want to find the x value so that y = 7
Looking at the graph, the x value when y = 7 is x=5
f(5) =7
The answer is the first answer choice
Nickels is 0,05 of dolar - n
dimes is 0,1 o dolar -d
quarters is 0,25 of dolar -q
dimes =2nickels
d=2n
quarters=2dimes
q=2d=4n
12,5=n(0,05)+2n(0,1)+4n(0,25)
12,5=0,05n+0,2n+n
12,5=1,25n
n=10
q=4n=40
There are 40 quarters
Some useful relations and identities:



By the first relation, we have

Applying the two latter identities, we get

We can apply the third identity again:

and this is probably as far as you have to go, but by no means is it the only possible solution.