Answer:
$12 in 12 $1 bills
Step-by-step explanation:
Let the number of $1 bills be x.
Amount of money in $1 bills is $x.
Alejandro has twice as many $1 bills than $20 bills, then Alejandro has [tex]\frac{x}{2}[/tex] $20 bills.
Amount of money in $20 bills is [tex]\$ \frac{x}{2}\cdot 20.[/tex]
Alejandro has 3 times as many $20 bills in his wallet as he has $5 bills, then Alejandro has [tex]\frac{x}{2}\div 3=\frac{x}{6}[/tex] $5 bills.
Amount of money in $5 bills is [tex]\$\frac{x}{6}\cdot 5.[/tex]
If he has a total of $142 in his wallet, then
[tex]x\cdot 1+\dfrac{x}{2}\cdot 20+\dfrac{x}{6}\cdot 5=142\\ \\x+10x+\dfrac{5x}{6}=142[/tex]
Multiply this equation by 6:
[tex]6x+60x+5x=142\cdot 6\\ \\71x=852\\ \\x=12[/tex]
