Sam is walking to joe’s house at a rate of 2 miles per hour. joe left his house at the same time and is walking at a rate of 1.5 miles per hour. if sam and joe live 7 miles apart, how long will it take for sam and joe to meet?

In order to answer this questions, let's suppose,

The time it takes for Sam and Joe to meet in hours= t
Joe's speed = 1.5miles/hour 
Sam's speed = 2 miles/hour
Distance between Joe and Sam = 7 miles
When they meet Joe covers a distance of J miles and Sam covers S miles
Now,
J+S=7
J=1.5 miles/hour *t
S= 2 miles/hour * t
1.5t + 2t =7
3.5 t = 7
t=2 hours
It will take 2 hours for Sam and Joe to meet