Question 7996
Since you don't know how many red cars there are, Red is X.
Since you do know how many blue cars there are, Blue is 2x+3 (twice red X plus 3) 
The total cars is 24. 
The equation is:
Factor the equation 
Subtract 3 from both sides 
 
Red x= 7
Blue 2(7)+3= 17
Total = 24 
I hope that helps you
CharStar