Question 947548
since it's 90km/h we make it 90km/1hour then multiply it by 4 on two sides so it become 360km/4hours now we remove 4 hours and replace it with 3 hours and it goes like 360km/3hours which equals 120km/h 
 90km/1hour
=360km/4hours
=90km/h 
so
360km/3hours
=120km/h