Answer:
8 tricycles
Explanation:
Let x be the amount of bicycles and y be the amount of tricycles
We can set up a system of equations:
x=3y+6
2x+3y=84
We can solve using substitution
2(3y+6)+3y=84
Distribute
6y+12+3y=84
Combine like terms
9y+12=84
Subtract 12 from both sides
9y=72
Divide 9 from both sides
y=8
There were 8 tricycles at the yard sale