Question

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

Answer 1

x - the total number of fish in the tank
6/7 of the fish in the tank have red stripes. 18 of the fish have red stripes.

$\frac{6}{7}x=18 \\ x=18 \times \frac{7}{6} \\ x=3 \times 7 \\ x=21$

There are 21 fish in the tank.