Let the number of nickles and dimes be x for nickles and y for dimes. if Jessica had twice as many nickles as dimes
then the number of nickles is two times the number of dimes and x = 2y .. This is you first equation
The combined number of nickles and dimes is $4.20. Therefore the second equation is
5 x + 10 y = 420 where 5 x is the value of the amount of nickles and 5 is the number of cents in a nickel
and 10 y is the value of the amount in dimes and 10 is the number of cents in a dime
please note that I converted the number of dollars $4.20 into cents 420
The two equations are:
x =2y
5x+ 10y = 420 solve by substitution method
substitute the x value of the first equation into the 2nd
5(2y) + 10y = 420, 10y + 10y = 420, 20 y = 420 , y = 420 / 20 = 21
x = 2(21) = 42 check
5 ( 42) + 10 ( 21) = 420, 210+210 = 420, 420 = 420 checks
Therefore Jessica had 42 nickles and 21 dimes
