At billy's school they have some bikes and some trikes with a total of 57 wheels. the number of bikes is three less than three times the number if trikes. How many bikes and trikes are there?
+33615 b = number of bikes, t = number of trikes
2*b + 3*t = 57 wheels
b = 3*t - 3
Substitute the 2nd equation into the first
2*(3*t - 3) + 3*t = 57 or
9t - 6 = 57 or
9t = 63 or
t = 7
Put this back into the 2nd equation;
b = 3*7 - 3 or
b = 18
So, in total: b + t = 25
.
