Question

Three-quarters of the boats in the marina are white, 4/7 of the remaining boats are blue, and the rest are red. If there are 9 red boats, how many boats are in the marina?

Answer 1

Answer: There are 84 boats.

Step-by-step explanation:

Let be "x" the number of boats in the marina.

According to the exercise,  $\frac{3}{4}$ of the boats are white. This is:

$\frac{3}{4}x$

You know that $\frac{4}{7}$ of the remaining boats are blue. This is:

$(1-\frac{3}{4})(\frac{4}{7})x=\frac{1}{7}x$

And the rest of the boats are red and there are 9 of them.

Knowing this, you can write the following expression:

$x-\frac{3}{4}x-\frac{1}{7}x=9$

Finally, you must solve for "x":

$\frac{3}{28}x=9\\\\x=(9)(\frac{28}{3})\\\\x=84$

Answer 2

84 because if 1/4 of the boats are divided into sevenths, that makes the whole marina a 28 part item. 3/28 are red so 84 is the total number of boats.