Question 333686
let b=number of bicycles
let t=number of tricycles
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given:  32 seats and 72 wheels
need:  b and t
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since each bicycle and each tricycle has one seat, there must be a total of 32 bicycles and tricycles:  
first equation:  b +t =32
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Since each bicycle has 2 wheels and each tricycle has 3 wheels
second equation:  2*b+3*t=72
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solve the first equation for one of the variables, say b
b=32-t
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substitute b=32-t into second equation
2*(32-t) +3*t = 72
64-2t+3t=72
64+t=72
t=8
and b=32-t=32-8=24
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there you go 8 tricycles and 24 bicycles