I stretched them a bit after they demonstrated they could create an improper or proper fraction with blocks. I wrote a mixed number which they said 'Easy peasy Ms. Rice.' Which was true. Then I asked if they could express it in one color and give me the improper and mixed number fraction.
Yup easy peasy.. then we began adding and subtracting all kinds of combinations of fractions with pattern blocks! This did take a leap but with prove it to me with blocks in one color before they wrote the mixed number helped and made it easier for many.
Subtraction required a bit more thinking & steps as we had to trade in and start with a single color. Adding was easy. We will be spending some more time on subtraction.
What amazed me was how fast some could do this all mentally now. They would just write the answer . So, I said prove it with the blocks And many did.