Question

12 I don't know how to set it up and I'm very confused

Answer 1

There are two things to solve for; the number of bicycles: b and tricycles: t. Solving for two things requires two equations. You are given enough information to set up:

an equation for number of cycles

b + t = 50

an equation for number of wheels

2b + 3t = 111

Now you can use substitution or elimination to solve for the first variable.

I'll use substitution.

b + t = 50 then b = 50 - t

So sub in (50 - t) for b in the second equation. This combines the two equations  into one and makes it in terms of only one variable.

2(50 - t)  + 3t = 111

100 - 2t + 3t = 111

100 + t = 111

t = 111 - 100

t = 11

Now use this in either of the equations to find the other variable, b.

11 + b = 50

b = 50 - 11

b = 39

Answer 2

Let B be the number of bicycle and T, the number of tricycle. Then:
 B+T = 50. If B have 2 wheels and T have 3, then the total
number of wheels is:
2B + 3T = 111.
Now from B+T = 50, let's find B→ B = 50-T. Plugin the value of B in
2B+3T = 111→→ 2(50-T) + 3T = 111
100 - 2T + 3T = 111
T = 111-100
And T = 11. If Tricycle = 11, then Bicycles = 50-11 = 39
Proof:
2(39) + 3(11) = 78 + 33 = 111