Suppose you flip a penny 50 times. with 28 tosses landing heads up. what percentage of the tosses would be heads? what percentage would be tails?

The best thing to do here is to put it into a fraction. as 28 landed heads up, 22 (50-28) must be tails. 
You can then put this into a fraction, which becomes 22/50.
To turn this into a decimal, you can then divide 1 by 50
1/50= 0.02
As you've got 22 lots of this, you then need to multiply 0.02 by 22.
0.2x22= 0.44
To find the percentage, you've then got to multiply the decimal by 100.
100x0.44= 44.
Therefore, 44% of the tosses would be tails

As you've found what one percentage is, you simply need to take this number away from 100 to find the other, rather than having to go through the process again.
100-44= 56
Therefore, 56% of the tosses would be heads.

Hope this helps :)