#### Answer

For approximately $3,300,000$ high school teenagers, social pressures and fitting in is the most important problem.

#### Work Step by Step

The graph shows data for $16,503,611$ students in the United States.
Out of those students, the graph shows that for $22\%$, social pressures and fitting in is the most important problem.
$22\%$ is approximately $20\%$, which is $\frac{20}{100}=\frac{1}{5}$; therefore, without using a calculator, we can estimate:
$16,500,000*\frac{1}{5}\approx3,300,000$
For about 3,300,000 high school teenagers, social pressures and fitting in is the most important problem.