Answer:
Sonya contributed $2,400 to the plan last year.
Explanation:
Sonya's employer matches 25% of Sonya's contribution to her 401(k) plan.
Sonya's employer contributed $600 to the plan last year.
Let Sonya's contribution to her 401(k) plan be = x
employer's contribution is 25% of x = 600
0.25x = 600
x = 600 ÷ 0.25 = $2,400
Therefore, Sonya contributed $2,400 to the plan last year.