Alex has 84 quarters and nickels worth a total of 17.80

Step-by-step explanation: An Equation To This Solution Would Be, 0.05 (84 - Q) + 0.25Q = 17.80

quarters = 68

nickels = 16

Step-by-step explanation:

Setting up a system of equations and using substitution to solve for each variable will give you the number of quarters and nickels:

q = number of quarters

n = number of nickels

q + n = 84

0.25q + 0.05n = 17.80

Solve the first equation for 'n':

n = 84 - q

Substitute the expression '84 - q' for 'n':

0.25q + 0.05 (84 - q) = 17.80

Distribute: 0.25q + 4.2 - 0.05q = 17.80

Combine like terms: 0.20q + 4.2 = 17.80

Subtract '4.2' from both sides: 0.20q + 4.2 - 4.2 = 17.80 - 4.2 or 0.2q = 13.60

Divide both sides by 0.2: 0.2q/0.2 = 13.60/0.2

Solve for 'q': q = 68

Use q = 68 to solve for n:

n = 84 - 68 = 16