Explain how to compare two ratios?

To compare ratios you have to find if the two ratios or fractions are the same. 
first you have to do cross multiplication. For ex: 6/12 and 1/2. Multiply 1 and 12, and multiply 2 and 6. if both sides equal 12 then they are equal (≈). But if they are not equall when you cross multiply then they are not equal (≠).

Re-do the question and enter the picture

N- 3 is the answer