me thank yu tri tu sae...faster kar go 300 miles & ohter kar go 240 miles
me assume yu meen both kars go same time-span
faster kar speed=(x+12)MPH
distans=speed*time, so faster kar...(x+12)*time=300 miles
sloe kar...x*time=240 miles...so time=(240 miles) / x
fast kar...(x+12)*(240/x)=300 miles
or 300x=240*(x+12)
(300/240)=(x+12)/x...1.25x=x+12
(1.25-1)x=12
x=12/0.25....x=4*12...x=48 MPH & x+12=60 MPH