10x-6y=0 -4x-6y=54 find the solution

Solve by addition/subtraction method

-10x-6y=0
-1(-4x-6y=54)
which changes to:
-10x-6y=0
4x+6y=-54
then we can solve for x:
-6x=-54
bring the -6 over by division to isolate "x"
x=9
chose one of the equations and replace the "x" with 9 to find the value of "y"
-10(9)-6y=0
-90-6y=0
-6y=90
y=-15

so the answer is (9,-15)

There is 240 red cars and there is 400 blue cars because 240/3=80 and 80*5=400