Out of 100 students in a class, 30% of students like to watch T.V. How many students don't like to watch T.V.?

Given: Total number of students = 100

Percentage of students who like to watch T.V. = 30%

Percentage of students who don't like to watch T.V. = 100% − 30% = 70%

∴ The number of students who don't like to watch T.V.

$=70\% \mathrm{of} 100$

$=\frac{70}{100}\times 100$

$=70$

Therefore, there are 70 students who don't like to watch TV.