Answer:
To solve the system of equations:
n + d = 21 ---(1)
0.05n + 0.10d = 1.70 ---(2)
We can use the substitution method by solving for one variable in terms of the other from equation (1) and substituting it into equation (2).
Solving equation (1) for n:
n = 21 - d
Substituting this expression for n into equation (2):
0.05(21 - d) + 0.10d = 1.70
Distributing the 0.05:
1.05 - 0.05d + 0.10d = 1.70
Combining like terms:
0.05d = 0.65
Dividing both sides by 0.05:
d = 13
Substituting this value of d into equation (1):
n + 13 = 21
Solving for n:
n = 8
Therefore, the solution to the system of equations is n = 8 and d = 13.