Can i get ? i don't understand can you explain it also

Let's look at what they give you...we don't know the number of quarters...but we have 4 times the number of dimes and 2 times the number of nickels...

quarters = .25x
dimes     =  4(.10)x    remember...4 times as many
nickels    =  2(.05)x                        2 times as many

this all equals $7.50

.25x + 4(.10)x + 2(.05)x = $7.50
.25x + .40x + .10x = $7.50
.75x = $7.50                              (divide by .75)
x = 10                              (this is how many quarters we have)

dimes = 4 times the quarters  (4 x 10 = 40 dimes)
nickels = 2 times the quarters (2 x 10 = 20 nickels)

so, we have 40 dimes, 20 nickels, and 10 quarters