I'm not sure if it only wants you to find Equation 1 or go further and solve:
x = the number of 5c coins
y = the number of 10c coins
Equation 1: the total number of coins is 65
x + y = 65
total value of $3.80
0.05x + 0.1y = 3.8
<u>Simultaneous Equations</u>
Make one coefficient the same
10 * (0.05x + 0.1y = 3.80 = 0.5x + y = 38
x + y = 65
0.5x + y = 38
Subtract the equations
(x + y) - (0.5x + y)= 65 - 38
(x - 0.5x) + (y - y) = 65 - 38
0.5x = 27
x = 54
Substitute it into the original equation to find y.
x + y = 65
54 + y = 56
y = 65 - 54 = 11
Substitute it into the other equation to check it's right.
0.05x + 0.1y = 3.8
0.05(54) + 0.1(65) = 3.8
x = 54 5c coins
y = 11 10c coins
