Marcos has 6 nickels and 9 quarters
Solution:
Let "n" be the number of nickels
Let "q" be the number of quarters
Marcos had 15 coins in nickels and quarters
Therefore, we can say,
number of nickels + number of quarters = 15
n + q = 15 -------- eqn 1
He has three more quarters than nickels
Number of quarters = 3 + number of nickels
q = 3 + n -------- eqn 2
Eqn 1 and eqn 2 represents the system of equations
Substitute eqn 2 in eqn 1
n + 3 + n = 15
2n + 3 = 15
2n = 15 - 3
2n = 12
n = 6
Substitute n = 6 in eqn 2
q = 3 + 6
q = 9
Thus Marcos has 6 nickels and 9 quarters