Consider the given equation:

Cross multiplying in the given equation, we get

Applying distributive property which states
, we get


Adding '4' on both the sides, we get


Subtracting '10n' from both the sides of the equation, we get


Dividing by '-8' in both the sides of the equation, we get

Therefore, the value of 'n' is -1.
164 times 5 is 820. 824 minus 820 is 4. Therefore there will be 4 marbles left
120.8. Make a proportion. 25/100 equals 30.2 over x, the number. Now cross multiply. 100 times 30.2 divided by 25, so it is 120.8.
Another way to reason this is to see that 25 percent is one fourth, so just do 30.2 times 4