Question 665386
let speed of car B be x km/h
speed of car A = x+20 km/h

distance = 315 km

time = 7 hours . 8am to 3 pm

since they are travelling towards each other, add up the speeds.

combined speed = x+x+20= 2x+20

d= s * t

315 = 7(2x+20)

315 = 14x+140

14x=315-140

14x= 175
/14
x= 175/14

x= 12.5 km/h    speed of car B

speed of car A = 12.5 + 20 = 32.5 km/h