At the end of the day, a scientist found she has 4/3 as many sample of Antarctic krill as she had for California copepods. She had a total of 84 samples. How many samples of copepods did she had?
Let's call the number of krill "x". Then the number of copepods is $${\frac{{\mathtt{4}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{x}}$$
together they total 84.
$$\frac{4}{3}x+x=84$$
$$\frac{7}{3}x=84$$
multiply both sides by 3/7
x=36 krill
