now, she made 1 and 1/4 quart of smoothie, she got thirsty and drank 1/5 of that, now how much is 1/5 of 1 and 1/4? well, just the product,
[tex]\bf 1\frac{1}{4}\implies \cfrac{1\cdot 4+1}{4}\implies \cfrac{5}{4}\qquad \qquad \qquad \qquad \cfrac{\underline{5}}{4}\cdot \cfrac{1}{\underline{5}}\implies \cfrac{1}{4}[/tex]
notice, is really just 5/4 of smoothie, she drank 1/4, so, what's leftover is 4/4 then, 5/4 - 1/4 is just 4/4, or really just 1.
now, her brothers drank the rest, well, the rest is 4/4, ok.... and each drank 1/3 of the smoothie, how many times does 1/3 go into 4/4?
[tex]\bf \cfrac{\quad \frac{4}{4}\quad }{\frac{1}{3}}\implies \cfrac{4}{4}\cdot \cfrac{3}{1}\implies 1\cdot \cfrac{3}{1}\implies \stackrel{brothers}{3}[/tex]
