Answer:
a.
b.
<em>A = 220 mm²</em>
<em>b = 20 mm</em>
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u = number of unicycles = number of wheels from all the unicycles
b = number of bikes
2*b = number of wheels from the bikes only
u+2b = total number of wheels (unicycles+bikes)
u+2b = 30 because there are 30 wheels overall
Answer is choice D
