A fan pushes a 500 g toycar 1m in 3 seconds how long would it take to push a 1000 g car 1m?

You need to learn the units. The newton is defined as kg-m/sec^2

f = 0.5 x 1/9 = 0.0555...N

Now do the other car the same way.

0.0555 = 1.000 x 1/t^2

t^2 = 1/0.0555

t = 4.24264 sec