James earns 20*.2=$<<20*.2=4>>4 less while working his second job
So he earns 20-4=$<<20-4=16>>16 an hour
At his first job he earns 20*30=$<<20*30=600>>600
He works 30/2=<<30/2=15>>15 hours at his second job
So he earns 15*16=$<<15*16=240>>240
So he earns 600+240=$<<600+240=840>>840 a week
#### 840