Posted by Kathryn on .
Last weekend, I went to play in the nearby park. It was real fun! I rode my new bicycle that Mom had gifted me on my birthday. On reaching the park, I saw that there were a total of 8 bicycles and tricycles. If the total number of wheels was 20, how many tricycles were there?

Math 
PsyDAG,
Let x = bikes and Y = trikes.
X + Y = 8
X = 8  Y
2X + 3Y = 20
Substitute 8Y for X.
2(8Y) + 3Y = 20
16  2Y + 3Y = 20
Y = 4
I hope this helps. Thanks for asking.