You answer is B because supplementary is 180°
30b + 100u = 900
5b + 25u = 200....multiply by -6
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30b + 100u = 900
-30b - 150u = - 1200 (result of multiplying by -6)
------------------add
-50u = - 300
u = 6 <== upgrated phones sold
30b + 100u = 900
30b + 100(6) = 900
30b + 600 = 900
30b = 900 - 600
30b = 300
b = 10 <== basic phones sold
200. 50x4=200 hope that helps
The answer than you are looking for is 53.84
