Answer:
0.12 x (x + 3000) = 4200
equation for her salary last year : last year's salary = (4200 / 0.12) - 3000
$32,000
Explanation:
Let x = last year's salary
this year's salary = 3000 + x
this equation can be used to determine how much she saved this year = 0.12 x (x + 3000) = 4200
to find last year's salary, make x the subject of the formula
4200 / 0.12 - 3000 = x
x = $32,000