Question 335411
Let F be the number of $5 bills, T the number of $10 bills.
1.{{{F=2T}}}
.
.
.
2.{{{5F+10T=540}}}
Substitute eq. 1 into eq. 2,
{{{5(2T)+10T=540}}}
{{{10T+10T=540}}}
{{{20T=540}}}
{{{highlight(T=27)}}}
Then from eq. 1,
{{{F=2T}}}
{{{highlight(F=54)}}}