Two cars start from two towns 400 miles apart and travel towards each other. They pass each other after 4 hours. find the speed of each car if the difference between their speeds is 20 miles per hour.

use an expression

s = speed of the slower car

then

(s+20) = speed of the faster car

When they meet is after 400 miles

Write distance equation

slow car d + fast car d = 400 mi

4s + 4 (s+20) = 400

8s + 80 = 400

8s = 400 - 80

8s = 320

s = 40 m/H