Question

Can you solve the equations and find the value of the missing number?

Answer 1

15 works, but it forces red and green to be the same:
Blue=6, 6+6+6=18
Red=3, 3+3+3=9
Green=3, 3x3-3=6
Blue x Red - Green = 6x3-3=15

Alternative answer would be 20. This allows for negative integers, which lets each colour be unique:
Blue=6, 6+6+6=18
Red=3, 3+3+3=9
Green=(-2), (-2)x(-2)-(-2)=6
Blue x Red - Green = 6x3-(-2)=20

Answer 2

ans 6x3-3=15

Answer 3

Thanks for the query.

3 Blue cars = 18 Therefore, 1 Blue car = 6
3 Red cars = 9 Therefore 1 Red car = 3
Now,

Green Car X Green Car - Green car = 6
Green car will have two values = 3 and -2
Since, there is no restrictions on negative numbers we will consider both the values.
Therefore there will be two answers
6 X 3 - 3 = 15
and
6 X 3 - (-2) = 20

Answer 4

6x3-3=15 the answer
For first ans it is 6+6+6=18
2nd- 3x3x3=9
3rd- 3x3-3=6

Answer 5

15
Answer

Blue car value = 6
Red car value = 3
Green car value =3
6×3-3=15