Question 54079
Draw a picture of Marion and Beth walking in opposite directions.
Can you see that if the are 30 miles apart you have to add their distances together to bet 30?  I hope so.
The only formula you need is distance (d)=rate (r)*time(t)
d=rt
Let Beth's rate=x
Then Marion's rate=x+1
The time for both= 2 
Your problem to solve is:
2(x+1)+2x=30
2x+2+2x=30
4x+2=30
4x+2-2=30-2
4x=28
4x/4=28/4
x=7
Beth's rate:x={{{highlight(7mph)}}}
Marion's rate:x+1=7+1={{{highlight(8mph)}}}
Check:2(7)+2(8)=30
14+16=30
30=30
Looks like we're right!
Happy Calculating!!!