<PRE><B>Question 854598</B>
r*t=d
(r-2)*t=9
(r-2*t=9
r*t-2*t=9

(r+2)*t=13
r*t+2*t=13
r*t-2*t=9
add
2r*t=22
r*t=22/2
r*t=11
ok
r*t-2*t=9
11-2*t=9
11-9=2*t
2=2*t
2/2=t
1=t
t=1 hour
r*1=11
r=11/1
r=11 mph
check
(r+c)*t=13
(11+2)*1=13
(13)*1=13
13=13

(r-c)*t=9
(11-c)*t=9
(11-2)*1=9
9*1=9
9=9
ok





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