a)
a+b=180 and a=2(b-30) using this in the first equation gives you:
2(b-30)+b=180
2b-60+b=180
3b-60=180
3b=240
b=80 so a=100
Andre's score was 100 and Brandon's score was 80.
b)
100x-200>50x-75 subtract 50x from both sides
50x-200>-75 add 200 to both sides
50x>125 divide both sides by 50
x>2.5