Answer
a. $W=2000+0.07s$ (current job)
$W=2300+0.05s$ (job offer)
b. The intersection of the two lines signifies how much you will have to sell at each job to get the same salary.
c. You should stick with your current job
Work Step by Step
a. At your current job, you get paid 2000 dollars a month plus 7% (0.07) commission. At your job offer, you get paid 2300 dollars a month plus 5% (0.05) commission.
b. Look at the intersection
c. $W=2000+0.07(20,000)$
$W=3400$ dollars per month at current job
$W=2300+0.05(20,000)$
$W=3300$ dollars per month at job offer