roy has 11 model cars that are all red or black. He has 3 more red cars than black cars. How many black cars does he have?
To solve this problem, let's use algebra. Let's assume the number of black cars is 'x'. Since Roy has 3 more red cars than black cars, the number of red cars would be 'x + 3'.
According to the problem, Roy has a total of 11 cars. Therefore, the equation would be:
x + (x + 3) = 11
To solve this equation, we combine like terms:
2x + 3 = 11
Subtracting 3 from both sides of the equation:
2x = 8
Next, divide both sides of the equation by 2:
x = 4
So, Roy has 4 black cars.