Question 502910
Maria has 20 coins in her pocket, all nickels and dimes. 
The total value of the coins is $1.35. How many of each type of coin does she have in her pocket?
:
let n = no. of nickels
let d = no. or dimes
;
Write an equation for each statement:
"Maria has 20 coins in her pocket, all nickels and dimes."
n + d = 20
n = (20-d), use this form for substitution
:
"The total value of the coins is $1.35."
.05n + .10d = 1.35
From the 1st statement, substitute n with (20-d)
.05(20-d) + .10d = 1.35
1 - .05d + .10d = 1.35
.05d = 1.35 - 1
.05d = .35
d = {{{.35/.05}}}
d = 7 dimes
:
You can find n, yourself, check that the total is 1.35