In the last two years, Mari grew 2 1/4 inches, Kim grew 2.4 inches, and Kate grew 2 1/8 inches. Write the amounts they grew in order from least to greatest

First, let's turn the fractions into decimal form so you can see the answer, more clearly. 
2 [tex] \frac{1}{4} [/tex] = 2.25
2.4 = 2.4
2 [tex] \frac{1}{8} [/tex] = 2.125

Now, after looking at the decimals, we can see which decimals are the biggest. They would order, from least to greatest, like this. 
1)  2.4
2) 2.25
3) 2.125

I hope this helps!