There is a video on khanacademy, search "rationalize the denominator." Then instead of getting the answer you will learn how to do it and be able to do it on other problems in the future.
Negative, You'll have to explain the why part though,
Answer:
1. 5 + y = 7
⇒ y = 7 - 5
⇒<u>y = 5</u>
2. 3.8 = a + 2.5
⇒ a = 2.5 - 3.8
⇒ <u>a = -1.3</u>
3. 5 + p = 9 1/3
⇒ p = 9 1/3 - 5
⇒ p = 28/3 - 5
⇒ p = 28/3 - 15/3
⇒ p = 13/3
⇒<u> </u><u>p = 4 1/3</u>
