Step-by-step explanation:
-6>t-(-13)
= -6>t+13
= -6-13>t
= -19>t
= t<-19
It gets repetitive really fast. The second verse is the same as the first. The result is ...

You type "they both ... " This indicates that there are TWO people involved, not just one.
"<span>plus 20% per month plus 15% commission" isn't quite clear. Is that 20% of the base pay ($1,250)? I assume that the 15% commission is figured on the sales ($20,000)
Please clarify this as much as you can.</span>
The answer is 32.5 aka 32 1/2.