Sasha has some pennies nickels and dimes in her pocket the number of coins is 18 the expression 0.01 p + 0.05 n + 0.10 d represents the value of the coins which is $1.14 she has twice as many dimes and pennies how many coins does sasha have?

A) p + n + d = 18
B) .01p + .05n + .10d = 1.14
C) 2p = d

Substituting C) into A)
A) p + n + 2p = 18 equals
A) 3p + n = 18
Substituting C) into B)
B) .01p + .05n + .10 *2p = 1.14
B) .01p + .05n + .2p = 1.14
B) .21p + .05n = 1.14  
Taking equation A)
A) 3p + n = 18 and multiplying it by -.05
A) -.15p -.05n = -.90  Then adding this to B)
B) .21p + .05n = 1.14
.06p = .24
Therefore there are 4 pennies.
(I'll leave it to you to determine the nickels and dimes.)

Oh what the heck, I'll finish it for you.

Looking at equation C)
C) 2p = d
We know there are 4 pennies so there are:
2 *4  = eight dimes
Looking at Equation A)
A) p + n + d = 18 we can fill in the pennies and the dimes:
A) 4 + n + 8 = 18
Therefore, there are 6 nickels.

i really dont know can u help me understand