Given:
savings 12% of her salary.
savings $4,200
This year's salary: x + 3,000
Last year's salary: x
4,200 represents 12% of her salary.
4,200 / 12% = 35,000 is her salary this year.
x + 3,000 = 35,000
x = 35,000 - 3,000
x = 32,000 her salary last year.