Question

in a fish tank 6/7 of the fish have a red stripe on them . if 18 of the fish have red stripes how many total fish are in the tank?

Answer 1

Well, if 6/7 is 18, and how many is the 7/7 or a 1 whole(total)?

$\bf \begin{array}{ccll} \stackrel{frational}{amount}&\stackrel{quantity}{amount}\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ \frac{6}{7}&18\\\\ \frac{7}{7}&x \end{array}\implies \cfrac{\frac{6}{7}}{\frac{7}{7}}=\cfrac{18}{x}\implies \cfrac{\frac{6}{7}}{1}=\cfrac{18}{x}\implies \cfrac{6}{7}=\cfrac{18}{x} \\\\\\ x=\cfrac{7\cdot 18}{6}$