Let x be the all sale for individual.
Determine the expression for total income of individual.
[tex]\frac{20}{100}x+40000=0.2x+40000[/tex]The total income was at least 70000. So last year income is 70000 or more than 70000.
Setermine the inequality for the sales.
[tex]\begin{gathered} 0.2x+40000-40000\ge70000-40000 \\ \frac{0.2x}{0.2}\ge\frac{30000}{0.2} \\ x\ge150000 \end{gathered}[/tex]