[titan_george]

I don't even know where to start with this question, but I am eager to learn how to answer it.

The question is: "A sample of Aluminum was heated to 150°C, then placed into 400. g of water at 20.9°C. The temperature of the water rose to 26.8°C. How many grams of Al were in the sample? (SAL = 0.9 J/g°C)

This is the formula we were given for the lesson: q=mc△T | The answer has to be rounded to significant numbers.

*I'm not looking for a quick answer, I actually want to learn the concept, please lead me into the right direction.
Thank you.

[Corribus]

You have to show your work to receive help. If you have done no work, then explain how you are approaching the problem conceptually. If you have no idea where to start conceptually, I recommend starting with the equation they give you. What does it mean?

[MNIO]

energy is conserved right?  so from an energy balance
  heat lost by aluminum = heat gained by water
or if you prefer
  heat lost by aluminum - heat gained by water = 0

********
for this problem
  heat is really Q = m * Cp * dT
so
  Q Al = Q H2O

you get to finish. Setup the problem, plug in the values.. .calculate away.