If all 20 were bikes, that would account for only40 wheels(20×2=40), but if 10 of those were trikes (10×3=30) and 10 were bikes (10×2=20) that would equal 50 wheels.

So your answer is 10 trikes and 10 bikes.

Not telling you the answer, but it helps.

variables: b = bikes, t = tricycles

assuming there are no left-over pedals/wheels, then

the “rules” of the system are:

2b + 2t = 40 (two pedals per bike or trike … 40 total)

2b + 3t = 50 (two wheels per pike, 3 per trike = 50)

either guess different values for b and t, or

if solving algebraically…

solve for b or t….. e.g., subtract equation (1) from (2)…