To find out how much Sonya contributed to her 401(k) plan last year, we can use the information about the employer's matching contribution.
The employer matches 25% of Sonya's contributions. If the employer contributed $600, we can set up the equation as follows:
Let \( x \) be Sonya's contribution. Then, the employer's contribution (which is 25% of \( x \)) can be represented as:
\[ 0.25x = 600 \]
To find \( x \), we can solve for it:
\[ x = \frac{600}{0.25} \]
Calculating that, we get:
\[ x = 600 \times 4 = 2400 \]
So, Sonya contributed $2400 to her 401(k) plan last year.