GMAT Data Sufficiency (DS) | Re: What is Sarah's annual income?

Let S = Sarah's annual income
Let M = Mary's annual income
Let x = the amount Sarah spends each year
Let y = the amount Mary spends each year

Rephrased target question: What is the value of S?

Statement 1: Sarah and Mary earn an annual income in the ratio of 4:3
In other words: S/M = 4:3
Cross multiply to get 3S = 4M
Simplify: 3S - 4M = 0
We can't find the value of S, so statement 1 is NOT SUFFICIENT

Statement 2: Sarah and Mary spend money in the ratio of 3:2 and together save $20,000,
...

---