Step-by-step explanation:
x: amount of five dollar bills
y: amount of one dollar bills
The sum of the amounts of each kind of bills is 18 and the sum of the value of all bills is 62. We can write a system of equations:

And we can solve using the elimination method. Substracting the first equation from the second:

Solving for x:

WIth x = 11 we can replace into the first equation and solve for y:

Answers:
She has:
• 11 five dollar bills
,
• 7 one dollar bills