Answer :
first off, let's convert the 20% to a fraction, so we can do so by simply dividing the percentage form by 100, 20/100 = 1/5, so 20% of whatever is really just 1/5 of that.
let's say the total amount is "x".
she deposited 1/5 of "x" in the bank, so she was left only holding
[tex]\bf x-\cfrac{1}{5}x\implies \cfrac{4}{5}x[/tex]
then she spent 1/5 of that remainder, and that happened to be 4800 bucks.
how much is 1/5 of (4/5)x? well is simply their product.
[tex]\bf \stackrel{\textit{remainder}}{\cfrac{4}{5}x}~~-~~\stackrel{\textit{one fifth of the remainder}}{\left(\cfrac{4}{5}x\cdot \cfrac{1}{5} \right)}~~=~~\stackrel{\textit{and that is}}{4800} \\\\\\ \cfrac{4x}{5}-\cfrac{4x}{25}=4800\implies \stackrel{\textit{multipliying both sides by }\stackrel{LCD}{25}}{25\left( \cfrac{4x}{5}-\cfrac{4x}{25} \right)=25(4800)} \\\\\\ 20x-4x=120000\implies 16x=120000\implies x=\cfrac{120000}{16}\implies x=7500[/tex]