The owner of a bike shop sells unicycles and bicycles and keeps inventory by counting seats and wheels. One day, she counts 21 s
eats and 30 wheels. The equation representing the total number of seats is u + b = 21 where u is the number of bicycles and b is the number of bicycles. A. 2u + b = 21
B. u + 2b = 30
C. 2u + b = 30
D. u + 2b = 21